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	$111.76	3.142%	$115.2715	$115.27	$115.25	$115.30
Purchase #2	$64.67	12.359%	$72.6626	$72.66	$72.65	$72.70
Purchase #3	$102.50	4.355%	$106.9639	$106.96	$106.95	$107.00
Purchase #4	$235.43	8.837%	$256.2349	$256.23	$256.25	$256.20
Purchase #5	$107.89	12.400%	$121.2684	$121.27	$121.25	$121.30
Purchase #6	$182.33	7.802%	$196.5554	$196.56	$196.55	$196.60
Purchase #7	$78.86	8.637%	$85.6711	$85.67	$85.65	$85.70
7 purchase totals =	$883.44		$954.6278	$954.62	$954.55	$954.80