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	$12.96	10.695%	$14.3461	$14.35	$14.35	$14.30
Purchase #2	$232.39	12.250%	$260.8578	$260.86	$260.85	$260.90
Purchase #3	$234.86	6.642%	$250.4594	$250.46	$250.45	$250.50
Purchase #4	$99.30	11.780%	$110.9975	$111.00	$111.00	$111.00
Purchase #5	$153.39	9.350%	$167.732	$167.73	$167.75	$167.70
Purchase #6	$21.30	13.144%	$24.0997	$24.10	$24.10	$24.10
Purchase #7	$223.82	12.302%	$251.3543	$251.35	$251.35	$251.40
7 purchase totals =	$978.02		$1,079.8468	$1,079.85	$1,079.85	$1,079.90