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	$158.69	7.856%	$171.1567	$171.16	$171.15	$171.20
Purchase #2	$188.83	3.471%	$195.3843	$195.38	$195.40	$195.40
Purchase #3	$248.59	3.178%	$256.4902	$256.49	$256.50	$256.50
Purchase #4	$186.33	3.314%	$192.505	$192.51	$192.50	$192.50
Purchase #5	$7.32	10.258%	$8.0709	$8.07	$8.05	$8.10
Purchase #6	$131.79	3.541%	$136.4567	$136.46	$136.45	$136.50
Purchase #7	$179.27	4.117%	$186.6505	$186.65	$186.65	$186.70
7 purchase totals =	$1,100.82		$1,146.7143	$1,146.72	$1,146.70	$1,146.90