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	$112.90	12.655%	$127.1875	$127.19	$127.20	$127.20
Purchase #2	$45.25	10.549%	$50.0234	$50.02	$50.00	$50.00
Purchase #3	$215.98	10.538%	$238.74	$238.74	$238.75	$238.70
Purchase #4	$209.60	9.410%	$229.3234	$229.32	$229.30	$229.30
Purchase #5	$7.39	5.360%	$7.7861	$7.79	$7.80	$7.80
Purchase #6	$228.67	11.549%	$255.0791	$255.08	$255.10	$255.10
Purchase #7	$244.91	7.733%	$263.8489	$263.85	$263.85	$263.80
7 purchase totals =	$1,064.70		$1,171.9884	$1,171.99	$1,172.00	$1,171.90