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	$179.50	3.585%	$185.9351	$185.94	$185.95	$185.90
Purchase #2	$236.92	3.178%	$244.4493	$244.45	$244.45	$244.40
Purchase #3	$92.89	10.640%	$102.7735	$102.77	$102.75	$102.80
Purchase #4	$106.25	11.168%	$118.116	$118.12	$118.10	$118.10
Purchase #5	$235.82	9.846%	$259.0388	$259.04	$259.05	$259.00
Purchase #6	$77.79	7.746%	$83.8156	$83.82	$83.80	$83.80
Purchase #7	$8.39	13.848%	$9.5518	$9.55	$9.55	$9.60
7 purchase totals =	$937.56		$1,003.6801	$1,003.69	$1,003.65	$1,003.60