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	$223.77	7.149%	$239.7673	$239.77	$239.75	$239.80
Purchase #2	$233.42	7.759%	$251.5311	$251.53	$251.55	$251.50
Purchase #3	$88.53	13.562%	$100.5364	$100.54	$100.55	$100.50
Purchase #4	$177.39	12.240%	$199.1025	$199.10	$199.10	$199.10
Purchase #5	$78.87	13.346%	$89.396	$89.40	$89.40	$89.40
Purchase #6	$240.69	13.483%	$273.1422	$273.14	$273.15	$273.10
Purchase #7	$168.92	7.598%	$181.7545	$181.75	$181.75	$181.80
7 purchase totals =	$1,211.59		$1,335.2300	$1,335.23	$1,335.25	$1,335.20