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	$237.28	5.379%	$250.0433	$250.04	$250.05	$250.00
Purchase #2	$27.42	4.258%	$28.5875	$28.59	$28.60	$28.60
Purchase #3	$167.93	12.813%	$189.4469	$189.45	$189.45	$189.40
Purchase #4	$241.99	9.295%	$264.483	$264.48	$264.50	$264.50
Purchase #5	$39.76	7.572%	$42.7706	$42.77	$42.75	$42.80
Purchase #6	$64.65	12.150%	$72.505	$72.51	$72.50	$72.50
Purchase #7	$10.98	4.637%	$11.4891	$11.49	$11.50	$11.50
7 purchase totals =	$790.01		$859.3254	$859.33	$859.35	$859.30