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	$85.64	4.658%	$89.6291	$89.63	$89.65	$89.60
Purchase #2	$54.65	3.191%	$56.3939	$56.39	$56.40	$56.40
Purchase #3	$188.33	13.748%	$214.2216	$214.22	$214.20	$214.20
Purchase #4	$14.33	8.238%	$15.5105	$15.51	$15.50	$15.50
Purchase #5	$75.58	7.814%	$81.4858	$81.49	$81.50	$81.50
Purchase #6	$245.42	13.354%	$278.1934	$278.19	$278.20	$278.20
Purchase #7	$83.43	7.747%	$89.8933	$89.89	$89.90	$89.90
7 purchase totals =	$747.38		$825.3276	$825.32	$825.35	$825.30