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	$237.45	11.415%	$264.5549	$264.55	$264.55	$264.60
Purchase #2	$74.48	3.401%	$77.0131	$77.01	$77.00	$77.00
Purchase #3	$228.38	5.250%	$240.37	$240.37	$240.35	$240.40
Purchase #4	$220.49	4.870%	$231.2279	$231.23	$231.25	$231.20
Purchase #5	$20.40	11.358%	$22.717	$22.72	$22.70	$22.70
Purchase #6	$42.29	7.856%	$45.6123	$45.61	$45.60	$45.60
Purchase #7	$165.60	11.619%	$184.8411	$184.84	$184.85	$184.80
7 purchase totals =	$989.09		$1,066.3363	$1,066.33	$1,066.30	$1,066.30