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	$30.50	5.726%	$32.2464	$32.25	$32.25	$32.20
Purchase #2	$67.27	8.314%	$72.8628	$72.86	$72.85	$72.90
Purchase #3	$225.30	7.654%	$242.5445	$242.54	$242.55	$242.50
Purchase #4	$38.76	12.494%	$43.6027	$43.60	$43.60	$43.60
Purchase #5	$37.26	4.641%	$38.9892	$38.99	$39.00	$39.00
Purchase #6	$175.69	8.230%	$190.1493	$190.15	$190.15	$190.10
Purchase #7	$174.61	5.611%	$184.4074	$184.41	$184.40	$184.40
7 purchase totals =	$749.39		$804.8023	$804.80	$804.80	$804.70