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	$165.80	5.611%	$175.103	$175.10	$175.10	$175.10
Purchase #2	$168.30	11.161%	$187.084	$187.08	$187.10	$187.10
Purchase #3	$84.62	5.375%	$89.1683	$89.17	$89.15	$89.20
Purchase #4	$247.53	6.608%	$263.8868	$263.89	$263.90	$263.90
Purchase #5	$156.46	5.151%	$164.5193	$164.52	$164.50	$164.50
Purchase #6	$110.49	11.681%	$123.3963	$123.40	$123.40	$123.40
Purchase #7	$129.39	10.551%	$143.0419	$143.04	$143.05	$143.00
7 purchase totals =	$1,062.59		$1,146.1996	$1,146.20	$1,146.20	$1,146.20