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	$185.45	10.223%	$204.4086	$204.41	$204.40	$204.40
Purchase #2	$109.50	7.800%	$118.041	$118.04	$118.05	$118.00
Purchase #3	$138.81	9.772%	$152.3745	$152.37	$152.35	$152.40
Purchase #4	$128.74	10.718%	$142.5384	$142.54	$142.55	$142.50
Purchase #5	$134.42	12.111%	$150.6996	$150.70	$150.70	$150.70
Purchase #6	$229.80	12.597%	$258.7479	$258.75	$258.75	$258.70
Purchase #7	$52.61	12.125%	$58.989	$58.99	$59.00	$59.00
7 purchase totals =	$979.33		$1,085.7990	$1,085.80	$1,085.80	$1,085.70