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	$71.51	3.147%	$73.7604	$73.76	$73.75	$73.80
Purchase #2	$144.62	13.693%	$164.4228	$164.42	$164.40	$164.40
Purchase #3	$180.94	13.383%	$205.1552	$205.16	$205.15	$205.20
Purchase #4	$189.86	10.576%	$209.9396	$209.94	$209.95	$209.90
Purchase #5	$127.29	7.264%	$136.5363	$136.54	$136.55	$136.50
Purchase #6	$123.35	4.386%	$128.7601	$128.76	$128.75	$128.80
Purchase #7	$225.98	4.574%	$236.3163	$236.32	$236.30	$236.30
7 purchase totals =	$1,063.55		$1,154.8907	$1,154.90	$1,154.85	$1,154.90