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	$149.81	11.147%	$166.5093	$166.51	$166.50	$166.50
Purchase #2	$152.57	6.346%	$162.2521	$162.25	$162.25	$162.30
Purchase #3	$229.30	7.780%	$247.1395	$247.14	$247.15	$247.10
Purchase #4	$91.29	3.663%	$94.634	$94.63	$94.65	$94.60
Purchase #5	$172.32	13.666%	$195.8693	$195.87	$195.85	$195.90
Purchase #6	$156.79	11.340%	$174.57	$174.57	$174.55	$174.60
Purchase #7	$38.83	7.133%	$41.5997	$41.60	$41.60	$41.60
7 purchase totals =	$990.91		$1,082.5739	$1,082.57	$1,082.55	$1,082.60