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	$171.68	5.276%	$180.7378	$180.74	$180.75	$180.70
Purchase #2	$235.79	4.118%	$245.4998	$245.50	$245.50	$245.50
Purchase #3	$79.90	12.143%	$89.6023	$89.60	$89.60	$89.60
Purchase #4	$33.72	6.463%	$35.8993	$35.90	$35.90	$35.90
Purchase #5	$171.65	11.570%	$191.5099	$191.51	$191.50	$191.50
Purchase #6	$130.63	8.586%	$141.8459	$141.85	$141.85	$141.80
Purchase #7	$168.45	12.330%	$189.2199	$189.22	$189.20	$189.20
7 purchase totals =	$991.82		$1,074.3149	$1,074.32	$1,074.30	$1,074.20