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	$54.66	10.178%	$60.2233	$60.22	$60.20	$60.20
Purchase #2	$146.27	4.732%	$153.1915	$153.19	$153.20	$153.20
Purchase #3	$59.60	13.769%	$67.8063	$67.81	$67.80	$67.80
Purchase #4	$7.27	8.373%	$7.8787	$7.88	$7.90	$7.90
Purchase #5	$133.33	12.719%	$150.2882	$150.29	$150.30	$150.30
Purchase #6	$79.84	6.109%	$84.7174	$84.72	$84.70	$84.70
Purchase #7	$86.96	4.213%	$90.6236	$90.62	$90.60	$90.60
7 purchase totals =	$567.93		$614.7290	$614.73	$614.70	$614.70