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	$171.93	6.283%	$182.7324	$182.73	$182.75	$182.70
Purchase #2	$49.38	12.346%	$55.4765	$55.48	$55.50	$55.50
Purchase #3	$234.90	12.222%	$263.6095	$263.61	$263.60	$263.60
Purchase #4	$95.56	10.825%	$105.9044	$105.90	$105.90	$105.90
Purchase #5	$172.57	7.644%	$185.7613	$185.76	$185.75	$185.80
Purchase #6	$135.54	8.746%	$147.3943	$147.39	$147.40	$147.40
Purchase #7	$249.98	8.275%	$270.6658	$270.67	$270.65	$270.70
7 purchase totals =	$1,109.86		$1,211.5442	$1,211.54	$1,211.55	$1,211.60