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	$56.45	4.696%	$59.1009	$59.10	$59.10	$59.10
Purchase #2	$84.98	10.294%	$93.7278	$93.73	$93.75	$93.70
Purchase #3	$134.42	9.701%	$147.4601	$147.46	$147.45	$147.50
Purchase #4	$30.60	12.294%	$34.362	$34.36	$34.35	$34.40
Purchase #5	$69.25	13.566%	$78.6445	$78.64	$78.65	$78.60
Purchase #6	$78.80	4.821%	$82.5989	$82.60	$82.60	$82.60
Purchase #7	$130.33	4.179%	$135.7765	$135.78	$135.80	$135.80
7 purchase totals =	$584.83		$631.6707	$631.67	$631.70	$631.70