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	$141.90	3.510%	$146.8807	$146.88	$146.90	$146.90
Purchase #2	$173.56	10.446%	$191.6901	$191.69	$191.70	$191.70
Purchase #3	$168.59	12.860%	$190.2707	$190.27	$190.25	$190.30
Purchase #4	$235.56	6.235%	$250.2472	$250.25	$250.25	$250.20
Purchase #5	$51.87	3.775%	$53.8281	$53.83	$53.85	$53.80
Purchase #6	$96.90	8.106%	$104.7547	$104.75	$104.75	$104.80
Purchase #7	$196.50	3.707%	$203.7843	$203.78	$203.80	$203.80
7 purchase totals =	$1,064.88		$1,141.4558	$1,141.45	$1,141.50	$1,141.50