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	$92.56	4.738%	$96.9455	$96.95	$96.95	$96.90
Purchase #2	$43.85	10.793%	$48.5827	$48.58	$48.60	$48.60
Purchase #3	$11.79	12.160%	$13.2237	$13.22	$13.20	$13.20
Purchase #4	$234.48	12.715%	$264.2941	$264.29	$264.30	$264.30
Purchase #5	$157.70	10.524%	$174.2963	$174.30	$174.30	$174.30
Purchase #6	$249.90	7.601%	$268.8949	$268.89	$268.90	$268.90
Purchase #7	$71.95	9.107%	$78.5025	$78.50	$78.50	$78.50
7 purchase totals =	$862.23		$944.7397	$944.73	$944.75	$944.70