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	$176.70	6.730%	$188.5919	$188.59	$188.60	$188.60
Purchase #2	$8.44	4.408%	$8.812	$8.81	$8.80	$8.80
Purchase #3	$79.97	13.639%	$90.8771	$90.88	$90.90	$90.90
Purchase #4	$229.99	7.236%	$246.6321	$246.63	$246.65	$246.60
Purchase #5	$99.63	6.311%	$105.9176	$105.92	$105.90	$105.90
Purchase #6	$64.61	12.609%	$72.7567	$72.76	$72.75	$72.80
Purchase #7	$64.34	11.659%	$71.8414	$71.84	$71.85	$71.80
7 purchase totals =	$723.68		$785.4288	$785.43	$785.45	$785.40