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	$142.96	8.667%	$155.3503	$155.35	$155.35	$155.40
Purchase #2	$167.90	4.523%	$175.4941	$175.49	$175.50	$175.50
Purchase #3	$51.57	3.586%	$53.4193	$53.42	$53.40	$53.40
Purchase #4	$149.77	10.541%	$165.5573	$165.56	$165.55	$165.60
Purchase #5	$159.39	9.514%	$174.5544	$174.55	$174.55	$174.60
Purchase #6	$246.48	7.316%	$264.5125	$264.51	$264.50	$264.50
Purchase #7	$86.46	5.353%	$91.0882	$91.09	$91.10	$91.10
7 purchase totals =	$1,004.53		$1,079.9761	$1,079.97	$1,079.95	$1,080.10