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	$243.35	10.658%	$269.2862	$269.29	$269.30	$269.30
Purchase #2	$72.92	3.208%	$75.2593	$75.26	$75.25	$75.30
Purchase #3	$233.93	12.836%	$263.9573	$263.96	$263.95	$264.00
Purchase #4	$242.88	7.820%	$261.8732	$261.87	$261.85	$261.90
Purchase #5	$128.41	3.517%	$132.9262	$132.93	$132.95	$132.90
Purchase #6	$64.58	10.405%	$71.2995	$71.30	$71.30	$71.30
Purchase #7	$88.43	12.265%	$99.2759	$99.28	$99.30	$99.30
7 purchase totals =	$1,074.50		$1,173.8776	$1,173.89	$1,173.90	$1,174.00