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	$229.66	7.534%	$246.9626	$246.96	$246.95	$247.00
Purchase #2	$86.36	5.505%	$91.1141	$91.11	$91.10	$91.10
Purchase #3	$35.80	11.846%	$40.0409	$40.04	$40.05	$40.00
Purchase #4	$96.30	7.265%	$103.2962	$103.30	$103.30	$103.30
Purchase #5	$33.53	10.450%	$37.0339	$37.03	$37.05	$37.00
Purchase #6	$156.36	12.245%	$175.5063	$175.51	$175.50	$175.50
Purchase #7	$83.82	6.826%	$89.5416	$89.54	$89.55	$89.50
7 purchase totals =	$721.83		$783.4956	$783.49	$783.50	$783.40