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	$54.25	13.663%	$61.6622	$61.66	$61.65	$61.70
Purchase #2	$165.85	6.618%	$176.826	$176.83	$176.85	$176.80
Purchase #3	$99.81	3.458%	$103.2614	$103.26	$103.25	$103.30
Purchase #4	$142.65	10.242%	$157.2602	$157.26	$157.25	$157.30
Purchase #5	$202.50	13.285%	$229.4021	$229.40	$229.40	$229.40
Purchase #6	$186.33	5.614%	$196.7906	$196.79	$196.80	$196.80
Purchase #7	$232.73	9.399%	$254.6043	$254.60	$254.60	$254.60
7 purchase totals =	$1,084.12		$1,179.8068	$1,179.80	$1,179.80	$1,179.90