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	$66.42	6.653%	$70.8389	$70.84	$70.85	$70.80
Purchase #2	$71.27	12.618%	$80.2628	$80.26	$80.25	$80.30
Purchase #3	$55.69	12.691%	$62.7576	$62.76	$62.75	$62.80
Purchase #4	$80.73	5.456%	$85.1346	$85.13	$85.15	$85.10
Purchase #5	$127.79	10.802%	$141.5939	$141.59	$141.60	$141.60
Purchase #6	$135.80	13.842%	$154.5974	$154.60	$154.60	$154.60
Purchase #7	$73.69	6.345%	$78.3656	$78.37	$78.35	$78.40
7 purchase totals =	$611.39		$673.5508	$673.55	$673.55	$673.60