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	$66.71	7.515%	$71.7233	$71.72	$71.70	$71.70
Purchase #2	$124.34	13.424%	$141.0314	$141.03	$141.05	$141.00
Purchase #3	$52.61	12.772%	$59.3293	$59.33	$59.35	$59.30
Purchase #4	$242.38	10.861%	$268.7049	$268.70	$268.70	$268.70
Purchase #5	$58.88	11.640%	$65.7336	$65.73	$65.75	$65.70
Purchase #6	$6.97	4.367%	$7.2744	$7.27	$7.25	$7.30
Purchase #7	$224.42	3.762%	$232.8627	$232.86	$232.85	$232.90
7 purchase totals =	$776.31		$846.6596	$846.64	$846.65	$846.60