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	$41.27	10.831%	$45.74	$45.74	$45.75	$45.70
Purchase #2	$234.69	4.480%	$245.2041	$245.20	$245.20	$245.20
Purchase #3	$193.53	4.661%	$202.5504	$202.55	$202.55	$202.60
Purchase #4	$88.97	13.118%	$100.6411	$100.64	$100.65	$100.60
Purchase #5	$148.89	10.533%	$164.5726	$164.57	$164.55	$164.60
Purchase #6	$223.48	13.532%	$253.7213	$253.72	$253.70	$253.70
Purchase #7	$88.43	9.139%	$96.5116	$96.51	$96.50	$96.50
7 purchase totals =	$1,019.26		$1,108.9411	$1,108.93	$1,108.90	$1,108.90