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	$118.65	5.366%	$125.0168	$125.02	$125.00	$125.00
Purchase #2	$83.53	7.495%	$89.7906	$89.79	$89.80	$89.80
Purchase #3	$33.83	6.187%	$35.9231	$35.92	$35.90	$35.90
Purchase #4	$178.58	10.243%	$196.8719	$196.87	$196.85	$196.90
Purchase #5	$11.38	11.478%	$12.6862	$12.69	$12.70	$12.70
Purchase #6	$229.91	6.294%	$244.3805	$244.38	$244.40	$244.40
Purchase #7	$28.50	4.723%	$29.8461	$29.85	$29.85	$29.80
7 purchase totals =	$684.38		$734.5152	$734.52	$734.50	$734.50