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	$160.86	9.320%	$175.8522	$175.85	$175.85	$175.90
Purchase #2	$196.71	13.643%	$223.5471	$223.55	$223.55	$223.50
Purchase #3	$101.72	13.288%	$115.2366	$115.24	$115.25	$115.20
Purchase #4	$55.60	12.781%	$62.7062	$62.71	$62.70	$62.70
Purchase #5	$174.82	12.604%	$196.8543	$196.85	$196.85	$196.90
Purchase #6	$40.82	12.497%	$45.9213	$45.92	$45.90	$45.90
Purchase #7	$53.93	8.263%	$58.3862	$58.39	$58.40	$58.40
7 purchase totals =	$784.46		$878.5039	$878.51	$878.50	$878.50