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	$103.43	13.692%	$117.5916	$117.59	$117.60	$117.60
Purchase #2	$141.58	4.586%	$148.0729	$148.07	$148.05	$148.10
Purchase #3	$92.51	4.163%	$96.3612	$96.36	$96.35	$96.40
Purchase #4	$142.77	7.580%	$153.592	$153.59	$153.60	$153.60
Purchase #5	$241.28	11.672%	$269.4422	$269.44	$269.45	$269.40
Purchase #6	$249.66	12.793%	$281.599	$281.60	$281.60	$281.60
Purchase #7	$116.32	11.373%	$129.5491	$129.55	$129.55	$129.50
7 purchase totals =	$1,087.55		$1,196.2080	$1,196.20	$1,196.20	$1,196.20