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	$159.97	7.197%	$171.483	$171.48	$171.50	$171.50
Purchase #2	$206.33	4.439%	$215.489	$215.49	$215.50	$215.50
Purchase #3	$78.34	3.694%	$81.2339	$81.23	$81.25	$81.20
Purchase #4	$143.72	8.751%	$156.2969	$156.30	$156.30	$156.30
Purchase #5	$94.62	10.811%	$104.8494	$104.85	$104.85	$104.80
Purchase #6	$211.46	12.668%	$238.2478	$238.25	$238.25	$238.20
Purchase #7	$81.62	4.465%	$85.2643	$85.26	$85.25	$85.30
7 purchase totals =	$976.06		$1,052.8643	$1,052.86	$1,052.90	$1,052.80