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	$90.34	7.123%	$96.7749	$96.77	$96.75	$96.80
Purchase #2	$136.37	11.420%	$151.9435	$151.94	$151.95	$151.90
Purchase #3	$141.58	7.572%	$152.3004	$152.30	$152.30	$152.30
Purchase #4	$154.68	6.116%	$164.1402	$164.14	$164.15	$164.10
Purchase #5	$135.29	6.502%	$144.0866	$144.09	$144.10	$144.10
Purchase #6	$133.59	6.375%	$142.1064	$142.11	$142.10	$142.10
Purchase #7	$218.83	4.198%	$228.0165	$228.02	$228.00	$228.00
7 purchase totals =	$1,010.68		$1,079.3685	$1,079.37	$1,079.35	$1,079.30