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	$93.89	4.186%	$97.8202	$97.82	$97.80	$97.80
Purchase #2	$106.41	4.632%	$111.3389	$111.34	$111.35	$111.30
Purchase #3	$174.40	9.268%	$190.5634	$190.56	$190.55	$190.60
Purchase #4	$132.54	8.446%	$143.7343	$143.73	$143.75	$143.70
Purchase #5	$76.99	6.742%	$82.1807	$82.18	$82.20	$82.20
Purchase #6	$247.26	6.818%	$264.1182	$264.12	$264.10	$264.10
Purchase #7	$234.83	4.118%	$244.5003	$244.50	$244.50	$244.50
7 purchase totals =	$1,066.32		$1,134.2560	$1,134.25	$1,134.25	$1,134.20