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	$162.67	4.629%	$170.2	$170.20	$170.20	$170.20
Purchase #2	$37.76	6.809%	$40.3311	$40.33	$40.35	$40.30
Purchase #3	$56.98	7.158%	$61.0586	$61.06	$61.05	$61.10
Purchase #4	$54.68	3.321%	$56.4959	$56.50	$56.50	$56.50
Purchase #5	$97.63	11.696%	$109.0488	$109.05	$109.05	$109.00
Purchase #6	$42.50	13.696%	$48.3208	$48.32	$48.30	$48.30
Purchase #7	$231.30	10.567%	$255.7415	$255.74	$255.75	$255.70
7 purchase totals =	$683.52		$741.1967	$741.20	$741.20	$741.10