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	$146.92	13.399%	$166.6058	$166.61	$166.60	$166.60
Purchase #2	$14.53	4.790%	$15.226	$15.23	$15.25	$15.20
Purchase #3	$122.30	3.705%	$126.8312	$126.83	$126.85	$126.80
Purchase #4	$69.41	3.218%	$71.6436	$71.64	$71.65	$71.60
Purchase #5	$74.55	5.839%	$78.903	$78.90	$78.90	$78.90
Purchase #6	$165.78	3.102%	$170.9225	$170.92	$170.90	$170.90
Purchase #7	$82.72	13.119%	$93.572	$93.57	$93.55	$93.60
7 purchase totals =	$676.21		$723.7041	$723.70	$723.70	$723.60