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	$149.71	4.637%	$156.6521	$156.65	$156.65	$156.70
Purchase #2	$210.30	3.480%	$217.6184	$217.62	$217.60	$217.60
Purchase #3	$169.45	6.765%	$180.9133	$180.91	$180.90	$180.90
Purchase #4	$207.88	4.308%	$216.8355	$216.84	$216.85	$216.80
Purchase #5	$69.25	13.413%	$78.5385	$78.54	$78.55	$78.50
Purchase #6	$137.87	13.539%	$156.5362	$156.54	$156.55	$156.50
Purchase #7	$109.73	6.639%	$117.015	$117.02	$117.00	$117.00
7 purchase totals =	$1,054.19		$1,124.1090	$1,124.12	$1,124.10	$1,124.00