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	$146.48	6.809%	$156.4538	$156.45	$156.45	$156.50
Purchase #2	$206.33	6.192%	$219.106	$219.11	$219.10	$219.10
Purchase #3	$121.38	3.610%	$125.7618	$125.76	$125.75	$125.80
Purchase #4	$225.38	3.515%	$233.3021	$233.30	$233.30	$233.30
Purchase #5	$112.45	4.323%	$117.3112	$117.31	$117.30	$117.30
Purchase #6	$85.73	4.126%	$89.2672	$89.27	$89.25	$89.30
Purchase #7	$148.64	7.291%	$159.4773	$159.48	$159.50	$159.50
7 purchase totals =	$1,046.39		$1,100.6794	$1,100.68	$1,100.65	$1,100.80