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	$112.43	13.460%	$127.5631	$127.56	$127.55	$127.60
Purchase #2	$164.72	5.781%	$174.2425	$174.24	$174.25	$174.20
Purchase #3	$207.30	8.693%	$225.3206	$225.32	$225.30	$225.30
Purchase #4	$232.95	4.572%	$243.6005	$243.60	$243.60	$243.60
Purchase #5	$18.70	12.207%	$20.9827	$20.98	$21.00	$21.00
Purchase #6	$90.74	6.568%	$96.6998	$96.70	$96.70	$96.70
Purchase #7	$100.59	11.230%	$111.8863	$111.89	$111.90	$111.90
7 purchase totals =	$927.43		$1,000.2955	$1,000.29	$1,000.30	$1,000.30