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	$60.47	12.315%	$67.9169	$67.92	$67.90	$67.90
Purchase #2	$173.88	4.625%	$181.922	$181.92	$181.90	$181.90
Purchase #3	$185.38	12.294%	$208.1706	$208.17	$208.15	$208.20
Purchase #4	$144.65	10.661%	$160.0711	$160.07	$160.05	$160.10
Purchase #5	$211.33	10.343%	$233.1879	$233.19	$233.20	$233.20
Purchase #6	$64.54	4.322%	$67.3294	$67.33	$67.35	$67.30
Purchase #7	$131.48	3.613%	$136.2304	$136.23	$136.25	$136.20
7 purchase totals =	$971.73		$1,054.8283	$1,054.83	$1,054.80	$1,054.80