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	$61.38	4.120%	$63.9089	$63.91	$63.90	$63.90
Purchase #2	$47.82	10.194%	$52.6948	$52.69	$52.70	$52.70
Purchase #3	$55.53	11.121%	$61.7055	$61.71	$61.70	$61.70
Purchase #4	$23.74	6.700%	$25.3306	$25.33	$25.35	$25.30
Purchase #5	$50.43	13.120%	$57.0464	$57.05	$57.05	$57.00
Purchase #6	$99.67	9.161%	$108.8008	$108.80	$108.80	$108.80
Purchase #7	$116.40	9.459%	$127.4103	$127.41	$127.40	$127.40
7 purchase totals =	$454.97		$496.8973	$496.90	$496.90	$496.80