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	$142.90	13.852%	$162.6945	$162.69	$162.70	$162.70
Purchase #2	$247.34	9.586%	$271.05	$271.05	$271.05	$271.10
Purchase #3	$42.47	9.723%	$46.5994	$46.60	$46.60	$46.60
Purchase #4	$40.94	4.599%	$42.8228	$42.82	$42.80	$42.80
Purchase #5	$124.52	5.788%	$131.7272	$131.73	$131.75	$131.70
Purchase #6	$189.84	7.837%	$204.7178	$204.72	$204.70	$204.70
Purchase #7	$223.40	4.464%	$233.3726	$233.37	$233.35	$233.40
7 purchase totals =	$1,011.41		$1,092.9843	$1,092.98	$1,092.95	$1,093.00