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	$241.72	9.464%	$264.5964	$264.60	$264.60	$264.60
Purchase #2	$89.25	13.519%	$101.3157	$101.32	$101.30	$101.30
Purchase #3	$169.91	13.152%	$192.2566	$192.26	$192.25	$192.30
Purchase #4	$38.25	10.102%	$42.114	$42.11	$42.10	$42.10
Purchase #5	$213.48	11.177%	$237.3407	$237.34	$237.35	$237.30
Purchase #6	$49.50	9.445%	$54.1753	$54.18	$54.20	$54.20
Purchase #7	$89.69	5.374%	$94.5099	$94.51	$94.50	$94.50
7 purchase totals =	$891.80		$986.3086	$986.32	$986.30	$986.30