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	$128.92	11.114%	$143.2482	$143.25	$143.25	$143.20
Purchase #2	$86.82	3.121%	$89.5297	$89.53	$89.55	$89.50
Purchase #3	$181.90	6.519%	$193.7581	$193.76	$193.75	$193.80
Purchase #4	$6.67	10.657%	$7.3808	$7.38	$7.40	$7.40
Purchase #5	$130.95	9.541%	$143.4439	$143.44	$143.45	$143.40
Purchase #6	$59.91	8.646%	$65.0898	$65.09	$65.10	$65.10
Purchase #7	$197.56	11.303%	$219.8902	$219.89	$219.90	$219.90
7 purchase totals =	$792.73		$862.3407	$862.34	$862.40	$862.30