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	$49.36	9.732%	$54.1637	$54.16	$54.15	$54.20
Purchase #2	$174.81	12.300%	$196.3116	$196.31	$196.30	$196.30
Purchase #3	$139.36	9.696%	$152.8723	$152.87	$152.85	$152.90
Purchase #4	$173.77	6.575%	$185.1954	$185.20	$185.20	$185.20
Purchase #5	$146.64	13.247%	$166.0654	$166.07	$166.05	$166.10
Purchase #6	$99.61	13.787%	$113.3432	$113.34	$113.35	$113.30
Purchase #7	$215.87	7.846%	$232.8072	$232.81	$232.80	$232.80
7 purchase totals =	$999.42		$1,100.7588	$1,100.76	$1,100.70	$1,100.80