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	$74.29	5.534%	$78.4012	$78.40	$78.40	$78.40
Purchase #2	$221.67	11.765%	$247.7495	$247.75	$247.75	$247.70
Purchase #3	$203.33	6.330%	$216.2008	$216.20	$216.20	$216.20
Purchase #4	$88.67	4.262%	$92.4491	$92.45	$92.45	$92.40
Purchase #5	$157.87	4.304%	$164.6647	$164.66	$164.65	$164.70
Purchase #6	$145.89	6.247%	$155.0037	$155.00	$155.00	$155.00
Purchase #7	$92.87	7.253%	$99.6059	$99.61	$99.60	$99.60
7 purchase totals =	$984.59		$1,054.0749	$1,054.07	$1,054.05	$1,054.00