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	$158.93	7.802%	$171.3297	$171.33	$171.35	$171.30
Purchase #2	$6.79	6.512%	$7.2322	$7.23	$7.25	$7.20
Purchase #3	$80.89	10.863%	$89.6771	$89.68	$89.70	$89.70
Purchase #4	$238.52	5.305%	$251.1735	$251.17	$251.15	$251.20
Purchase #5	$109.82	3.355%	$113.5045	$113.50	$113.50	$113.50
Purchase #6	$112.61	13.175%	$127.4464	$127.45	$127.45	$127.40
Purchase #7	$210.90	10.323%	$232.6712	$232.67	$232.65	$232.70
7 purchase totals =	$918.46		$993.0346	$993.03	$993.05	$993.00