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	$188.63	6.754%	$201.3701	$201.37	$201.35	$201.40
Purchase #2	$84.27	6.550%	$89.7897	$89.79	$89.80	$89.80
Purchase #3	$49.63	10.117%	$54.6511	$54.65	$54.65	$54.70
Purchase #4	$56.26	11.139%	$62.5268	$62.53	$62.55	$62.50
Purchase #5	$67.89	7.863%	$73.2282	$73.23	$73.25	$73.20
Purchase #6	$246.45	4.228%	$256.8699	$256.87	$256.85	$256.90
Purchase #7	$42.73	7.470%	$45.9219	$45.92	$45.90	$45.90
7 purchase totals =	$735.86		$784.3577	$784.36	$784.35	$784.40