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	$97.53	3.594%	$101.0352	$101.04	$101.05	$101.00
Purchase #2	$227.58	13.836%	$259.068	$259.07	$259.05	$259.10
Purchase #3	$51.71	7.640%	$55.6606	$55.66	$55.65	$55.70
Purchase #4	$103.58	7.448%	$111.2946	$111.29	$111.30	$111.30
Purchase #5	$141.83	13.739%	$161.316	$161.32	$161.30	$161.30
Purchase #6	$65.67	9.440%	$71.8692	$71.87	$71.85	$71.90
Purchase #7	$242.70	9.156%	$264.9216	$264.92	$264.90	$264.90
7 purchase totals =	$930.60		$1,025.1652	$1,025.17	$1,025.10	$1,025.20