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	$153.65	11.303%	$171.0171	$171.02	$171.00	$171.00
Purchase #2	$107.46	10.323%	$118.5531	$118.55	$118.55	$118.60
Purchase #3	$103.53	7.196%	$110.98	$110.98	$111.00	$111.00
Purchase #4	$160.61	4.150%	$167.2753	$167.28	$167.30	$167.30
Purchase #5	$208.39	11.850%	$233.0842	$233.08	$233.10	$233.10
Purchase #6	$119.43	6.752%	$127.4939	$127.49	$127.50	$127.50
Purchase #7	$143.72	10.576%	$158.9198	$158.92	$158.90	$158.90
7 purchase totals =	$996.79		$1,087.3234	$1,087.32	$1,087.35	$1,087.40