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	$187.78	4.496%	$196.2226	$196.22	$196.20	$196.20
Purchase #2	$87.88	6.638%	$93.7135	$93.71	$93.70	$93.70
Purchase #3	$42.28	10.526%	$46.7304	$46.73	$46.75	$46.70
Purchase #4	$68.88	9.354%	$75.323	$75.32	$75.30	$75.30
Purchase #5	$241.77	11.192%	$268.8289	$268.83	$268.85	$268.80
Purchase #6	$89.43	11.548%	$99.7574	$99.76	$99.75	$99.80
Purchase #7	$158.76	8.520%	$172.2864	$172.29	$172.30	$172.30
7 purchase totals =	$876.78		$952.8622	$952.86	$952.85	$952.80