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	$159.25	7.747%	$171.5871	$171.59	$171.60	$171.60
Purchase #2	$195.41	7.700%	$210.4566	$210.46	$210.45	$210.50
Purchase #3	$120.40	5.256%	$126.7282	$126.73	$126.75	$126.70
Purchase #4	$130.60	12.153%	$146.4718	$146.47	$146.45	$146.50
Purchase #5	$149.95	12.161%	$168.1854	$168.19	$168.20	$168.20
Purchase #6	$162.95	5.364%	$171.6906	$171.69	$171.70	$171.70
Purchase #7	$72.95	13.648%	$82.9062	$82.91	$82.90	$82.90
7 purchase totals =	$991.51		$1,078.0259	$1,078.04	$1,078.05	$1,078.10