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	$147.31	8.367%	$159.6354	$159.64	$159.65	$159.60
Purchase #2	$116.37	13.787%	$132.4139	$132.41	$132.40	$132.40
Purchase #3	$61.37	10.151%	$67.5997	$67.60	$67.60	$67.60
Purchase #4	$13.91	4.730%	$14.5679	$14.57	$14.55	$14.60
Purchase #5	$181.42	10.671%	$200.7793	$200.78	$200.80	$200.80
Purchase #6	$185.77	12.580%	$209.1399	$209.14	$209.15	$209.10
Purchase #7	$95.58	9.131%	$104.3074	$104.31	$104.30	$104.30
7 purchase totals =	$801.73		$888.4435	$888.45	$888.45	$888.40