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	$137.83	10.474%	$152.2663	$152.27	$152.25	$152.30
Purchase #2	$189.91	4.856%	$199.132	$199.13	$199.15	$199.10
Purchase #3	$142.49	4.239%	$148.5302	$148.53	$148.55	$148.50
Purchase #4	$57.67	11.243%	$64.1538	$64.15	$64.15	$64.20
Purchase #5	$22.51	13.543%	$25.5585	$25.56	$25.55	$25.60
Purchase #6	$188.59	4.168%	$196.4504	$196.45	$196.45	$196.50
Purchase #7	$134.30	11.793%	$150.138	$150.14	$150.15	$150.10
7 purchase totals =	$873.30		$936.2292	$936.23	$936.25	$936.30