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	$90.46	7.354%	$97.1124	$97.11	$97.10	$97.10
Purchase #2	$66.95	6.297%	$71.1658	$71.17	$71.15	$71.20
Purchase #3	$78.32	9.873%	$86.0525	$86.05	$86.05	$86.10
Purchase #4	$148.62	13.474%	$168.6451	$168.65	$168.65	$168.60
Purchase #5	$203.89	11.862%	$228.0754	$228.08	$228.10	$228.10
Purchase #6	$122.61	4.273%	$127.8491	$127.85	$127.85	$127.80
Purchase #7	$44.66	13.381%	$50.636	$50.64	$50.65	$50.60
7 purchase totals =	$755.51		$829.5363	$829.55	$829.55	$829.50