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	$168.78	3.350%	$174.4341	$174.43	$174.45	$174.40
Purchase #2	$215.95	11.370%	$240.5035	$240.50	$240.50	$240.50
Purchase #3	$120.94	10.417%	$133.5383	$133.54	$133.55	$133.50
Purchase #4	$159.28	13.443%	$180.692	$180.69	$180.70	$180.70
Purchase #5	$37.88	5.712%	$40.0437	$40.04	$40.05	$40.00
Purchase #6	$158.56	9.308%	$173.3188	$173.32	$173.30	$173.30
Purchase #7	$67.79	10.855%	$75.1486	$75.15	$75.15	$75.10
7 purchase totals =	$929.18		$1,017.6790	$1,017.67	$1,017.70	$1,017.50