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	$44.50	5.263%	$46.842	$46.84	$46.85	$46.80
Purchase #2	$104.89	7.784%	$113.0546	$113.05	$113.05	$113.10
Purchase #3	$104.85	5.386%	$110.4972	$110.50	$110.50	$110.50
Purchase #4	$117.57	5.421%	$123.9435	$123.94	$123.95	$123.90
Purchase #5	$24.38	12.131%	$27.3375	$27.34	$27.35	$27.30
Purchase #6	$177.40	6.482%	$188.8991	$188.90	$188.90	$188.90
Purchase #7	$109.79	12.172%	$123.1536	$123.15	$123.15	$123.20
7 purchase totals =	$683.38		$733.7275	$733.72	$733.75	$733.70