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	$81.63	13.107%	$92.3292	$92.33	$92.35	$92.30
Purchase #2	$39.31	6.463%	$41.8506	$41.85	$41.85	$41.90
Purchase #3	$205.81	7.814%	$221.892	$221.89	$221.90	$221.90
Purchase #4	$26.38	13.332%	$29.897	$29.90	$29.90	$29.90
Purchase #5	$75.72	13.289%	$85.7824	$85.78	$85.80	$85.80
Purchase #6	$174.96	7.125%	$187.4259	$187.43	$187.45	$187.40
Purchase #7	$145.34	9.562%	$159.2374	$159.24	$159.25	$159.20
7 purchase totals =	$749.15		$818.4145	$818.42	$818.50	$818.40