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	$141.37	12.823%	$159.4979	$159.50	$159.50	$159.50
Purchase #2	$116.38	10.712%	$128.8466	$128.85	$128.85	$128.80
Purchase #3	$22.40	13.402%	$25.402	$25.40	$25.40	$25.40
Purchase #4	$186.82	6.386%	$198.7503	$198.75	$198.75	$198.80
Purchase #5	$196.56	12.574%	$221.2755	$221.28	$221.30	$221.30
Purchase #6	$35.44	6.272%	$37.6628	$37.66	$37.65	$37.70
Purchase #7	$233.36	8.828%	$253.961	$253.96	$253.95	$254.00
7 purchase totals =	$932.33		$1,025.3961	$1,025.40	$1,025.40	$1,025.50