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	$39.56	13.541%	$44.9168	$44.92	$44.90	$44.90
Purchase #2	$74.48	3.415%	$77.0235	$77.02	$77.00	$77.00
Purchase #3	$111.36	5.198%	$117.1485	$117.15	$117.15	$117.10
Purchase #4	$224.80	8.293%	$243.4427	$243.44	$243.45	$243.40
Purchase #5	$216.67	12.806%	$244.4168	$244.42	$244.40	$244.40
Purchase #6	$90.52	6.716%	$96.5993	$96.60	$96.60	$96.60
Purchase #7	$56.43	6.117%	$59.8818	$59.88	$59.90	$59.90
7 purchase totals =	$813.82		$883.4294	$883.43	$883.40	$883.30