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	$177.48	7.504%	$190.7981	$190.80	$190.80	$190.80
Purchase #2	$169.31	7.281%	$181.6375	$181.64	$181.65	$181.60
Purchase #3	$202.53	6.264%	$215.2165	$215.22	$215.20	$215.20
Purchase #4	$37.34	10.453%	$41.2432	$41.24	$41.25	$41.20
Purchase #5	$162.47	10.412%	$179.3864	$179.39	$179.40	$179.40
Purchase #6	$164.49	12.714%	$185.4033	$185.40	$185.40	$185.40
Purchase #7	$141.76	8.734%	$154.1413	$154.14	$154.15	$154.10
7 purchase totals =	$1,055.38		$1,147.8263	$1,147.83	$1,147.85	$1,147.70