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	$36.85	12.670%	$41.5189	$41.52	$41.50	$41.50
Purchase #2	$88.76	3.618%	$91.9713	$91.97	$91.95	$92.00
Purchase #3	$142.71	10.597%	$157.833	$157.83	$157.85	$157.80
Purchase #4	$239.74	10.268%	$264.3565	$264.36	$264.35	$264.40
Purchase #5	$147.75	3.191%	$152.4647	$152.46	$152.45	$152.50
Purchase #6	$247.41	10.523%	$273.445	$273.45	$273.45	$273.40
Purchase #7	$142.36	12.423%	$160.0454	$160.05	$160.05	$160.00
7 purchase totals =	$1,045.58		$1,141.6348	$1,141.64	$1,141.60	$1,141.60