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	$69.36	4.266%	$72.3189	$72.32	$72.30	$72.30
Purchase #2	$78.33	5.869%	$82.9272	$82.93	$82.95	$82.90
Purchase #3	$159.84	13.722%	$181.7732	$181.77	$181.75	$181.80
Purchase #4	$103.48	11.702%	$115.5892	$115.59	$115.60	$115.60
Purchase #5	$18.91	9.391%	$20.6858	$20.69	$20.70	$20.70
Purchase #6	$120.29	4.807%	$126.0723	$126.07	$126.05	$126.10
Purchase #7	$217.49	13.616%	$247.1034	$247.10	$247.10	$247.10
7 purchase totals =	$767.70		$846.4700	$846.47	$846.45	$846.50