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	$239.91	4.497%	$250.6988	$250.70	$250.70	$250.70
Purchase #2	$50.27	6.781%	$53.6788	$53.68	$53.70	$53.70
Purchase #3	$81.39	13.170%	$92.1091	$92.11	$92.10	$92.10
Purchase #4	$72.54	13.767%	$82.5266	$82.53	$82.55	$82.50
Purchase #5	$53.60	10.373%	$59.1599	$59.16	$59.15	$59.20
Purchase #6	$92.76	10.744%	$102.7261	$102.73	$102.75	$102.70
Purchase #7	$209.66	11.831%	$234.4649	$234.46	$234.45	$234.50
7 purchase totals =	$800.13		$875.3642	$875.37	$875.40	$875.40