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	$145.52	4.696%	$152.3536	$152.35	$152.35	$152.40
Purchase #2	$106.55	12.833%	$120.2236	$120.22	$120.20	$120.20
Purchase #3	$79.98	9.364%	$87.4693	$87.47	$87.45	$87.50
Purchase #4	$99.70	4.753%	$104.4387	$104.44	$104.45	$104.40
Purchase #5	$128.48	6.766%	$137.173	$137.17	$137.15	$137.20
Purchase #6	$246.81	7.567%	$265.4861	$265.49	$265.50	$265.50
Purchase #7	$245.27	13.709%	$278.8941	$278.89	$278.90	$278.90
7 purchase totals =	$1,052.31		$1,146.0384	$1,146.03	$1,146.00	$1,146.10