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	$40.41	13.702%	$45.947	$45.95	$45.95	$45.90
Purchase #2	$176.44	4.841%	$184.9815	$184.98	$185.00	$185.00
Purchase #3	$243.44	8.147%	$263.2731	$263.27	$263.25	$263.30
Purchase #4	$195.72	8.539%	$212.4325	$212.43	$212.45	$212.40
Purchase #5	$70.49	13.510%	$80.0132	$80.01	$80.00	$80.00
Purchase #6	$81.27	11.731%	$90.8038	$90.80	$90.80	$90.80
Purchase #7	$77.92	10.799%	$86.3346	$86.33	$86.35	$86.30
7 purchase totals =	$885.69		$963.7857	$963.77	$963.80	$963.70