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	$94.95	3.830%	$98.5866	$98.59	$98.60	$98.60
Purchase #2	$131.76	7.841%	$142.0913	$142.09	$142.10	$142.10
Purchase #3	$64.87	10.497%	$71.6794	$71.68	$71.70	$71.70
Purchase #4	$80.50	11.484%	$89.7446	$89.74	$89.75	$89.70
Purchase #5	$223.53	10.727%	$247.5081	$247.51	$247.50	$247.50
Purchase #6	$96.84	4.607%	$101.3014	$101.30	$101.30	$101.30
Purchase #7	$233.71	13.800%	$265.962	$265.96	$265.95	$266.00
7 purchase totals =	$926.16		$1,016.8734	$1,016.87	$1,016.90	$1,016.90