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	$124.80	4.651%	$130.6044	$130.60	$130.60	$130.60
Purchase #2	$241.31	5.787%	$255.2746	$255.27	$255.25	$255.30
Purchase #3	$10.63	11.156%	$11.8159	$11.82	$11.80	$11.80
Purchase #4	$97.43	12.414%	$109.525	$109.53	$109.55	$109.50
Purchase #5	$115.87	5.213%	$121.9103	$121.91	$121.90	$121.90
Purchase #6	$125.92	4.720%	$131.8634	$131.86	$131.85	$131.90
Purchase #7	$178.44	5.113%	$187.5636	$187.56	$187.55	$187.60
7 purchase totals =	$894.40		$948.5572	$948.55	$948.50	$948.60