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	$95.45	3.463%	$98.7554	$98.76	$98.75	$98.80
Purchase #2	$149.94	12.516%	$168.7065	$168.71	$168.70	$168.70
Purchase #3	$63.95	5.463%	$67.4436	$67.44	$67.45	$67.40
Purchase #4	$191.47	8.102%	$206.9829	$206.98	$207.00	$207.00
Purchase #5	$65.71	9.138%	$71.7146	$71.71	$71.70	$71.70
Purchase #6	$47.92	5.529%	$50.5695	$50.57	$50.55	$50.60
Purchase #7	$79.34	3.733%	$82.3018	$82.30	$82.30	$82.30
7 purchase totals =	$693.78		$746.4743	$746.47	$746.45	$746.50