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	$172.35	7.364%	$185.0419	$185.04	$185.05	$185.00
Purchase #2	$196.27	11.638%	$219.1119	$219.11	$219.10	$219.10
Purchase #3	$223.86	13.495%	$254.0699	$254.07	$254.05	$254.10
Purchase #4	$135.36	7.622%	$145.6771	$145.68	$145.70	$145.70
Purchase #5	$233.80	12.736%	$263.5768	$263.58	$263.60	$263.60
Purchase #6	$127.35	3.588%	$131.9193	$131.92	$131.90	$131.90
Purchase #7	$7.38	6.116%	$7.8314	$7.83	$7.85	$7.80
7 purchase totals =	$1,096.37		$1,207.2283	$1,207.23	$1,207.25	$1,207.20