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	$163.86	5.148%	$172.2955	$172.30	$172.30	$172.30
Purchase #2	$90.38	5.474%	$95.3274	$95.33	$95.35	$95.30
Purchase #3	$55.70	8.581%	$60.4796	$60.48	$60.50	$60.50
Purchase #4	$184.39	3.744%	$191.2936	$191.29	$191.30	$191.30
Purchase #5	$12.44	11.314%	$13.8475	$13.85	$13.85	$13.80
Purchase #6	$203.29	3.756%	$210.9256	$210.93	$210.95	$210.90
Purchase #7	$35.36	6.398%	$37.6223	$37.62	$37.60	$37.60
7 purchase totals =	$745.42		$781.7915	$781.80	$781.85	$781.70