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	$86.85	11.515%	$96.8508	$96.85	$96.85	$96.90
Purchase #2	$63.37	12.730%	$71.437	$71.44	$71.45	$71.40
Purchase #3	$18.25	12.433%	$20.519	$20.52	$20.50	$20.50
Purchase #4	$47.29	9.697%	$51.8757	$51.88	$51.90	$51.90
Purchase #5	$86.33	11.727%	$96.4539	$96.45	$96.45	$96.50
Purchase #6	$44.29	5.124%	$46.5594	$46.56	$46.55	$46.60
Purchase #7	$148.75	11.479%	$165.825	$165.83	$165.85	$165.80
7 purchase totals =	$495.13		$549.5208	$549.53	$549.55	$549.60