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	$91.33	6.483%	$97.2509	$97.25	$97.25	$97.30
Purchase #2	$101.29	11.862%	$113.305	$113.31	$113.30	$113.30
Purchase #3	$68.58	4.179%	$71.446	$71.45	$71.45	$71.40
Purchase #4	$12.72	6.280%	$13.5188	$13.52	$13.50	$13.50
Purchase #5	$209.82	9.571%	$229.9019	$229.90	$229.90	$229.90
Purchase #6	$229.36	8.853%	$249.6652	$249.67	$249.65	$249.70
Purchase #7	$216.62	11.217%	$240.9183	$240.92	$240.90	$240.90
7 purchase totals =	$929.72		$1,016.0061	$1,016.02	$1,015.95	$1,016.00