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	$212.57	10.136%	$234.1161	$234.12	$234.10	$234.10
Purchase #2	$243.43	12.653%	$274.2312	$274.23	$274.25	$274.20
Purchase #3	$91.41	5.854%	$96.7611	$96.76	$96.75	$96.80
Purchase #4	$148.40	13.281%	$168.109	$168.11	$168.10	$168.10
Purchase #5	$231.92	10.726%	$256.7957	$256.80	$256.80	$256.80
Purchase #6	$177.27	4.674%	$185.5556	$185.56	$185.55	$185.60
Purchase #7	$112.25	9.774%	$123.2213	$123.22	$123.20	$123.20
7 purchase totals =	$1,217.25		$1,338.7900	$1,338.80	$1,338.75	$1,338.80