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	$184.90	13.341%	$209.5675	$209.57	$209.55	$209.60
Purchase #2	$16.76	4.231%	$17.4691	$17.47	$17.45	$17.50
Purchase #3	$69.28	12.737%	$78.1042	$78.10	$78.10	$78.10
Purchase #4	$137.49	7.265%	$147.4786	$147.48	$147.50	$147.50
Purchase #5	$110.31	12.535%	$124.1374	$124.14	$124.15	$124.10
Purchase #6	$81.54	12.232%	$91.514	$91.51	$91.50	$91.50
Purchase #7	$148.83	13.799%	$169.3671	$169.37	$169.35	$169.40
7 purchase totals =	$749.11		$837.6379	$837.64	$837.60	$837.70