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	$51.69	4.217%	$53.8698	$53.87	$53.85	$53.90
Purchase #2	$228.29	7.377%	$245.131	$245.13	$245.15	$245.10
Purchase #3	$31.25	3.208%	$32.2525	$32.25	$32.25	$32.30
Purchase #4	$46.51	7.389%	$49.9466	$49.95	$49.95	$49.90
Purchase #5	$238.81	10.866%	$264.7591	$264.76	$264.75	$264.80
Purchase #6	$182.56	7.401%	$196.0713	$196.07	$196.05	$196.10
Purchase #7	$72.67	10.333%	$80.179	$80.18	$80.20	$80.20
7 purchase totals =	$851.78		$922.2093	$922.21	$922.20	$922.30