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	$168.90	12.253%	$189.5953	$189.60	$189.60	$189.60
Purchase #2	$66.48	6.384%	$70.7241	$70.72	$70.70	$70.70
Purchase #3	$183.89	11.239%	$204.5574	$204.56	$204.55	$204.60
Purchase #4	$142.59	13.638%	$162.0364	$162.04	$162.05	$162.00
Purchase #5	$199.66	8.335%	$216.3017	$216.30	$216.30	$216.30
Purchase #6	$61.89	7.451%	$66.5014	$66.50	$66.50	$66.50
Purchase #7	$149.64	12.207%	$167.9066	$167.91	$167.90	$167.90
7 purchase totals =	$973.05		$1,077.6229	$1,077.63	$1,077.60	$1,077.60