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	$228.46	3.507%	$236.4721	$236.47	$236.45	$236.50
Purchase #2	$84.72	5.675%	$89.5279	$89.53	$89.55	$89.50
Purchase #3	$187.87	4.765%	$196.822	$196.82	$196.80	$196.80
Purchase #4	$85.92	4.275%	$89.5931	$89.59	$89.60	$89.60
Purchase #5	$88.66	12.691%	$99.9118	$99.91	$99.90	$99.90
Purchase #6	$155.97	5.834%	$165.0693	$165.07	$165.05	$165.10
Purchase #7	$118.68	12.236%	$133.2017	$133.20	$133.20	$133.20
7 purchase totals =	$950.28		$1,010.5979	$1,010.59	$1,010.55	$1,010.60