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	$102.91	5.845%	$108.9251	$108.93	$108.95	$108.90
Purchase #2	$154.36	5.289%	$162.5241	$162.52	$162.50	$162.50
Purchase #3	$147.62	10.243%	$162.7407	$162.74	$162.75	$162.70
Purchase #4	$64.89	4.334%	$67.7023	$67.70	$67.70	$67.70
Purchase #5	$63.33	12.707%	$71.3773	$71.38	$71.40	$71.40
Purchase #6	$214.42	4.316%	$223.6744	$223.67	$223.65	$223.70
Purchase #7	$196.79	6.833%	$210.2367	$210.24	$210.25	$210.20
7 purchase totals =	$944.32		$1,007.1806	$1,007.18	$1,007.20	$1,007.10