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	$249.76	10.415%	$275.7725	$275.77	$275.75	$275.80
Purchase #2	$236.62	9.618%	$259.3781	$259.38	$259.40	$259.40
Purchase #3	$35.39	13.351%	$40.1149	$40.11	$40.10	$40.10
Purchase #4	$134.98	7.385%	$144.9483	$144.95	$144.95	$144.90
Purchase #5	$185.98	12.851%	$209.8803	$209.88	$209.90	$209.90
Purchase #6	$81.50	7.579%	$87.6769	$87.68	$87.70	$87.70
Purchase #7	$37.31	9.502%	$40.8552	$40.86	$40.85	$40.90
7 purchase totals =	$961.54		$1,058.6262	$1,058.63	$1,058.65	$1,058.70