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	$172.89	7.758%	$186.3028	$186.30	$186.30	$186.30
Purchase #2	$98.49	8.517%	$106.8784	$106.88	$106.90	$106.90
Purchase #3	$47.26	6.389%	$50.2794	$50.28	$50.30	$50.30
Purchase #4	$163.79	12.507%	$184.2752	$184.28	$184.30	$184.30
Purchase #5	$90.86	10.178%	$100.1077	$100.11	$100.10	$100.10
Purchase #6	$126.52	13.362%	$143.4256	$143.43	$143.45	$143.40
Purchase #7	$98.33	4.763%	$103.0135	$103.01	$103.00	$103.00
7 purchase totals =	$798.14		$874.2826	$874.29	$874.35	$874.30