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	$198.37	10.156%	$218.5165	$218.52	$218.50	$218.50
Purchase #2	$211.70	12.639%	$238.4568	$238.46	$238.45	$238.50
Purchase #3	$233.71	4.219%	$243.5702	$243.57	$243.55	$243.60
Purchase #4	$243.81	6.389%	$259.387	$259.39	$259.40	$259.40
Purchase #5	$102.49	3.739%	$106.3221	$106.32	$106.30	$106.30
Purchase #6	$232.69	5.429%	$245.3227	$245.32	$245.30	$245.30
Purchase #7	$204.65	5.210%	$215.3123	$215.31	$215.30	$215.30
7 purchase totals =	$1,427.42		$1,526.8876	$1,526.89	$1,526.80	$1,526.90