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	$218.25	12.343%	$245.1886	$245.19	$245.20	$245.20
Purchase #2	$147.27	11.575%	$164.3165	$164.32	$164.30	$164.30
Purchase #3	$31.58	11.610%	$35.2464	$35.25	$35.25	$35.20
Purchase #4	$57.30	3.645%	$59.3886	$59.39	$59.40	$59.40
Purchase #5	$147.79	7.644%	$159.0871	$159.09	$159.10	$159.10
Purchase #6	$149.98	7.262%	$160.8715	$160.87	$160.85	$160.90
Purchase #7	$200.73	10.522%	$221.8508	$221.85	$221.85	$221.90
7 purchase totals =	$952.90		$1,045.9495	$1,045.96	$1,045.95	$1,046.00