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	$62.89	5.304%	$66.2257	$66.23	$66.25	$66.20
Purchase #2	$69.41	3.550%	$71.8741	$71.87	$71.85	$71.90
Purchase #3	$172.78	7.358%	$185.4932	$185.49	$185.50	$185.50
Purchase #4	$119.37	11.519%	$133.1202	$133.12	$133.10	$133.10
Purchase #5	$191.70	12.282%	$215.2446	$215.24	$215.25	$215.20
Purchase #6	$243.96	11.557%	$272.1545	$272.15	$272.15	$272.20
Purchase #7	$147.88	3.167%	$152.5634	$152.56	$152.55	$152.60
7 purchase totals =	$1,007.99		$1,096.6757	$1,096.66	$1,096.65	$1,096.70