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	$88.76	3.352%	$91.7352	$91.74	$91.75	$91.70
Purchase #2	$24.95	11.856%	$27.9081	$27.91	$27.90	$27.90
Purchase #3	$30.36	5.808%	$32.1233	$32.12	$32.10	$32.10
Purchase #4	$48.47	11.622%	$54.1032	$54.10	$54.10	$54.10
Purchase #5	$86.45	3.287%	$89.2916	$89.29	$89.30	$89.30
Purchase #6	$20.27	7.202%	$21.7298	$21.73	$21.75	$21.70
Purchase #7	$88.33	3.139%	$91.1027	$91.10	$91.10	$91.10
7 purchase totals =	$387.59		$407.9939	$407.99	$408.00	$407.90