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	$173.59	5.343%	$182.8649	$182.86	$182.85	$182.90
Purchase #2	$204.48	3.345%	$211.3199	$211.32	$211.30	$211.30
Purchase #3	$89.67	6.452%	$95.4555	$95.46	$95.45	$95.50
Purchase #4	$84.33	12.535%	$94.9008	$94.90	$94.90	$94.90
Purchase #5	$131.88	4.446%	$137.7434	$137.74	$137.75	$137.70
Purchase #6	$69.39	13.107%	$78.4849	$78.48	$78.50	$78.50
Purchase #7	$114.94	12.366%	$129.1535	$129.15	$129.15	$129.20
7 purchase totals =	$868.28		$929.9229	$929.91	$929.90	$930.00