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	$222.88	6.483%	$237.3293	$237.33	$237.35	$237.30
Purchase #2	$245.66	10.682%	$271.9014	$271.90	$271.90	$271.90
Purchase #3	$146.27	12.395%	$164.4002	$164.40	$164.40	$164.40
Purchase #4	$76.35	11.502%	$85.1318	$85.13	$85.15	$85.10
Purchase #5	$210.65	5.525%	$222.2884	$222.29	$222.30	$222.30
Purchase #6	$220.72	10.208%	$243.2511	$243.25	$243.25	$243.30
Purchase #7	$194.34	10.843%	$215.4123	$215.41	$215.40	$215.40
7 purchase totals =	$1,316.87		$1,439.7145	$1,439.71	$1,439.75	$1,439.70