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	$190.47	7.234%	$204.2486	$204.25	$204.25	$204.20
Purchase #2	$6.85	9.159%	$7.4774	$7.48	$7.50	$7.50
Purchase #3	$174.72	4.281%	$182.1998	$182.20	$182.20	$182.20
Purchase #4	$227.33	3.572%	$235.4502	$235.45	$235.45	$235.50
Purchase #5	$88.92	11.869%	$99.4739	$99.47	$99.45	$99.50
Purchase #6	$242.25	12.488%	$272.5022	$272.50	$272.50	$272.50
Purchase #7	$153.76	9.655%	$168.6055	$168.61	$168.60	$168.60
7 purchase totals =	$1,084.30		$1,169.9576	$1,169.96	$1,169.95	$1,170.00