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	$144.63	4.693%	$151.4175	$151.42	$151.40	$151.40
Purchase #2	$178.70	5.299%	$188.1693	$188.17	$188.15	$188.20
Purchase #3	$34.28	9.269%	$37.4574	$37.46	$37.45	$37.50
Purchase #4	$70.36	5.369%	$74.1376	$74.14	$74.15	$74.10
Purchase #5	$96.61	8.196%	$104.5282	$104.53	$104.55	$104.50
Purchase #6	$209.61	13.825%	$238.5886	$238.59	$238.60	$238.60
Purchase #7	$91.56	12.338%	$102.8567	$102.86	$102.85	$102.90
7 purchase totals =	$825.75		$897.1553	$897.17	$897.15	$897.20