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	$209.45	8.609%	$227.4816	$227.48	$227.50	$227.50
Purchase #2	$35.35	5.303%	$37.2246	$37.22	$37.20	$37.20
Purchase #3	$71.43	12.851%	$80.6095	$80.61	$80.60	$80.60
Purchase #4	$55.68	6.236%	$59.1522	$59.15	$59.15	$59.20
Purchase #5	$221.93	5.402%	$233.9187	$233.92	$233.90	$233.90
Purchase #6	$89.68	6.727%	$95.7128	$95.71	$95.70	$95.70
Purchase #7	$168.30	5.368%	$177.3343	$177.33	$177.35	$177.30
7 purchase totals =	$851.82		$911.4337	$911.42	$911.40	$911.40