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	$44.32	7.130%	$47.48	$47.48	$47.50	$47.50
Purchase #2	$190.86	6.655%	$203.5617	$203.56	$203.55	$203.60
Purchase #3	$79.83	7.457%	$85.7829	$85.78	$85.80	$85.80
Purchase #4	$53.78	10.429%	$59.3887	$59.39	$59.40	$59.40
Purchase #5	$154.80	13.126%	$175.119	$175.12	$175.10	$175.10
Purchase #6	$92.60	10.825%	$102.624	$102.62	$102.60	$102.60
Purchase #7	$181.27	13.141%	$205.0907	$205.09	$205.10	$205.10
7 purchase totals =	$797.46		$879.0470	$879.04	$879.05	$879.10