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	$79.83	13.532%	$90.6326	$90.63	$90.65	$90.60
Purchase #2	$194.49	9.180%	$212.3442	$212.34	$212.35	$212.30
Purchase #3	$233.62	7.468%	$251.0667	$251.07	$251.05	$251.10
Purchase #4	$89.40	3.474%	$92.5058	$92.51	$92.50	$92.50
Purchase #5	$70.27	13.310%	$79.6229	$79.62	$79.60	$79.60
Purchase #6	$134.89	10.846%	$149.5202	$149.52	$149.50	$149.50
Purchase #7	$221.35	5.686%	$233.936	$233.94	$233.95	$233.90
7 purchase totals =	$1,023.85		$1,109.6284	$1,109.63	$1,109.60	$1,109.50