Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$165.71	3.550%	$171.5927	$171.59	$171.60	$171.60
Purchase #2	$187.42	6.453%	$199.5142	$199.51	$199.50	$199.50
Purchase #3	$112.29	3.744%	$116.4941	$116.49	$116.50	$116.50
Purchase #4	$127.65	3.362%	$131.9416	$131.94	$131.95	$131.90
Purchase #5	$135.74	10.690%	$150.2506	$150.25	$150.25	$150.30
Purchase #6	$158.74	10.731%	$175.7744	$175.77	$175.75	$175.80
Purchase #7	$156.61	13.383%	$177.5691	$177.57	$177.55	$177.60
7 purchase totals =	$1,044.16		$1,123.1367	$1,123.12	$1,123.10	$1,123.20