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	$82.44	4.545%	$86.1869	$86.19	$86.20	$86.20
Purchase #2	$142.30	7.234%	$152.594	$152.59	$152.60	$152.60
Purchase #3	$232.59	7.773%	$250.6692	$250.67	$250.65	$250.70
Purchase #4	$242.44	8.209%	$262.3419	$262.34	$262.35	$262.30
Purchase #5	$118.31	10.497%	$130.729	$130.73	$130.75	$130.70
Purchase #6	$123.89	11.288%	$137.8747	$137.87	$137.85	$137.90
Purchase #7	$118.96	6.869%	$127.1314	$127.13	$127.15	$127.10
7 purchase totals =	$1,060.93		$1,147.5271	$1,147.52	$1,147.55	$1,147.50