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	$45.41	4.403%	$47.4094	$47.41	$47.40	$47.40
Purchase #2	$54.42	13.805%	$61.9327	$61.93	$61.95	$61.90
Purchase #3	$40.56	13.160%	$45.8977	$45.90	$45.90	$45.90
Purchase #4	$78.86	10.235%	$86.9313	$86.93	$86.95	$86.90
Purchase #5	$140.65	10.720%	$155.7277	$155.73	$155.75	$155.70
Purchase #6	$90.32	6.689%	$96.3615	$96.36	$96.35	$96.40
Purchase #7	$15.26	3.552%	$15.802	$15.80	$15.80	$15.80
7 purchase totals =	$465.48		$510.0623	$510.06	$510.10	$510.00