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	$198.88	7.767%	$214.327	$214.33	$214.35	$214.30
Purchase #2	$191.36	9.642%	$209.8109	$209.81	$209.80	$209.80
Purchase #3	$146.74	10.707%	$162.4515	$162.45	$162.45	$162.50
Purchase #4	$93.66	8.823%	$101.9236	$101.92	$101.90	$101.90
Purchase #5	$27.81	12.489%	$31.2832	$31.28	$31.30	$31.30
Purchase #6	$216.60	9.616%	$237.4283	$237.43	$237.45	$237.40
Purchase #7	$99.44	12.223%	$111.5946	$111.59	$111.60	$111.60
7 purchase totals =	$974.49		$1,068.8191	$1,068.81	$1,068.85	$1,068.80