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	$137.65	8.870%	$149.8596	$149.86	$149.85	$149.90
Purchase #2	$181.94	5.255%	$191.5009	$191.50	$191.50	$191.50
Purchase #3	$121.77	5.380%	$128.3212	$128.32	$128.30	$128.30
Purchase #4	$224.27	13.421%	$254.3693	$254.37	$254.35	$254.40
Purchase #5	$57.76	11.351%	$64.3163	$64.32	$64.30	$64.30
Purchase #6	$250.57	5.624%	$264.6621	$264.66	$264.65	$264.70
Purchase #7	$35.52	5.568%	$37.4978	$37.50	$37.50	$37.50
7 purchase totals =	$1,009.48		$1,090.5272	$1,090.53	$1,090.45	$1,090.60