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	$246.86	8.728%	$268.4059	$268.41	$268.40	$268.40
Purchase #2	$10.82	13.143%	$12.2421	$12.24	$12.25	$12.20
Purchase #3	$59.53	9.228%	$65.0234	$65.02	$65.00	$65.00
Purchase #4	$72.44	5.762%	$76.614	$76.61	$76.60	$76.60
Purchase #5	$100.86	13.479%	$114.4549	$114.45	$114.45	$114.50
Purchase #6	$219.37	13.428%	$248.827	$248.83	$248.85	$248.80
Purchase #7	$29.32	13.752%	$33.3521	$33.35	$33.35	$33.40
7 purchase totals =	$739.20		$818.9194	$818.91	$818.90	$818.90