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	$52.85	12.563%	$59.4895	$59.49	$59.50	$59.50
Purchase #2	$225.40	5.168%	$237.0487	$237.05	$237.05	$237.00
Purchase #3	$109.33	5.108%	$114.9146	$114.91	$114.90	$114.90
Purchase #4	$243.54	5.267%	$256.3673	$256.37	$256.35	$256.40
Purchase #5	$162.53	11.675%	$181.5054	$181.51	$181.50	$181.50
Purchase #6	$32.61	13.581%	$37.0388	$37.04	$37.05	$37.00
Purchase #7	$54.96	6.216%	$58.3763	$58.38	$58.40	$58.40
7 purchase totals =	$881.22		$944.7406	$944.75	$944.75	$944.70