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	$175.59	13.240%	$198.8381	$198.84	$198.85	$198.80
Purchase #2	$237.79	5.341%	$250.4904	$250.49	$250.50	$250.50
Purchase #3	$137.27	8.744%	$149.2729	$149.27	$149.25	$149.30
Purchase #4	$87.98	10.572%	$97.2812	$97.28	$97.30	$97.30
Purchase #5	$81.37	10.789%	$90.149	$90.15	$90.15	$90.10
Purchase #6	$96.82	5.190%	$101.845	$101.85	$101.85	$101.80
Purchase #7	$158.41	10.740%	$175.4232	$175.42	$175.40	$175.40
7 purchase totals =	$975.23		$1,063.2998	$1,063.30	$1,063.30	$1,063.20