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	$67.39	8.506%	$73.1222	$73.12	$73.10	$73.10
Purchase #2	$203.89	7.480%	$219.141	$219.14	$219.15	$219.10
Purchase #3	$83.44	7.683%	$89.8507	$89.85	$89.85	$89.90
Purchase #4	$247.85	11.297%	$275.8496	$275.85	$275.85	$275.80
Purchase #5	$9.64	5.222%	$10.1434	$10.14	$10.15	$10.10
Purchase #6	$159.49	3.687%	$165.3704	$165.37	$165.35	$165.40
Purchase #7	$109.52	5.363%	$115.3936	$115.39	$115.40	$115.40
7 purchase totals =	$881.22		$948.8709	$948.86	$948.85	$948.80