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	$152.43	5.449%	$160.7359	$160.74	$160.75	$160.70
Purchase #2	$83.31	7.865%	$89.8623	$89.86	$89.85	$89.90
Purchase #3	$27.60	7.167%	$29.5781	$29.58	$29.60	$29.60
Purchase #4	$73.66	6.182%	$78.2137	$78.21	$78.20	$78.20
Purchase #5	$175.57	6.700%	$187.3332	$187.33	$187.35	$187.30
Purchase #6	$156.83	13.183%	$177.5049	$177.50	$177.50	$177.50
Purchase #7	$156.48	6.403%	$166.4994	$166.50	$166.50	$166.50
7 purchase totals =	$825.88		$889.7275	$889.72	$889.75	$889.70