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	$194.93	13.849%	$221.9259	$221.93	$221.95	$221.90
Purchase #2	$68.45	11.870%	$76.575	$76.58	$76.60	$76.60
Purchase #3	$249.72	6.471%	$265.8794	$265.88	$265.90	$265.90
Purchase #4	$142.32	3.757%	$147.667	$147.67	$147.65	$147.70
Purchase #5	$202.46	10.399%	$223.5138	$223.51	$223.50	$223.50
Purchase #6	$155.50	11.107%	$172.7714	$172.77	$172.75	$172.80
Purchase #7	$162.82	7.413%	$174.8898	$174.89	$174.90	$174.90
7 purchase totals =	$1,176.20		$1,283.2223	$1,283.23	$1,283.25	$1,283.30