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	$94.73	11.565%	$105.6855	$105.69	$105.70	$105.70
Purchase #2	$33.92	10.842%	$37.5976	$37.60	$37.60	$37.60
Purchase #3	$47.82	11.414%	$53.2782	$53.28	$53.30	$53.30
Purchase #4	$88.68	9.279%	$96.9086	$96.91	$96.90	$96.90
Purchase #5	$217.51	11.448%	$242.4105	$242.41	$242.40	$242.40
Purchase #6	$250.42	5.550%	$264.3183	$264.32	$264.30	$264.30
Purchase #7	$243.50	12.579%	$274.1299	$274.13	$274.15	$274.10
7 purchase totals =	$976.58		$1,074.3286	$1,074.34	$1,074.35	$1,074.30