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	$91.27	3.808%	$94.7456	$94.75	$94.75	$94.70
Purchase #2	$140.70	13.614%	$159.8549	$159.85	$159.85	$159.90
Purchase #3	$187.90	10.842%	$208.2721	$208.27	$208.25	$208.30
Purchase #4	$56.98	7.711%	$61.3737	$61.37	$61.35	$61.40
Purchase #5	$248.53	8.817%	$270.4429	$270.44	$270.45	$270.40
Purchase #6	$197.29	7.404%	$211.8974	$211.90	$211.90	$211.90
Purchase #7	$73.52	6.412%	$78.2341	$78.23	$78.25	$78.20
7 purchase totals =	$996.19		$1,084.8207	$1,084.81	$1,084.80	$1,084.80