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	$187.59	3.745%	$194.6152	$194.62	$194.60	$194.60
Purchase #2	$171.74	11.704%	$191.8404	$191.84	$191.85	$191.80
Purchase #3	$112.43	6.272%	$119.4816	$119.48	$119.50	$119.50
Purchase #4	$219.98	13.684%	$250.0821	$250.08	$250.10	$250.10
Purchase #5	$157.93	11.218%	$175.6466	$175.65	$175.65	$175.60
Purchase #6	$38.28	4.761%	$40.1025	$40.10	$40.10	$40.10
Purchase #7	$91.55	7.604%	$98.5115	$98.51	$98.50	$98.50
7 purchase totals =	$979.50		$1,070.2799	$1,070.28	$1,070.30	$1,070.20