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	$240.25	5.352%	$253.1082	$253.11	$253.10	$253.10
Purchase #2	$121.99	12.411%	$137.1302	$137.13	$137.15	$137.10
Purchase #3	$89.99	6.664%	$95.9869	$95.99	$96.00	$96.00
Purchase #4	$238.67	4.843%	$250.2288	$250.23	$250.25	$250.20
Purchase #5	$54.32	3.614%	$56.2831	$56.28	$56.30	$56.30
Purchase #6	$142.36	6.499%	$151.612	$151.61	$151.60	$151.60
Purchase #7	$118.35	7.436%	$127.1505	$127.15	$127.15	$127.20
7 purchase totals =	$1,005.93		$1,071.4997	$1,071.50	$1,071.55	$1,071.50