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	$96.98	4.120%	$100.9756	$100.98	$101.00	$101.00
Purchase #2	$168.48	12.639%	$189.7742	$189.77	$189.75	$189.80
Purchase #3	$80.46	12.723%	$90.6969	$90.70	$90.70	$90.70
Purchase #4	$124.56	11.315%	$138.654	$138.65	$138.65	$138.70
Purchase #5	$145.75	4.506%	$152.3175	$152.32	$152.30	$152.30
Purchase #6	$192.26	3.754%	$199.4774	$199.48	$199.50	$199.50
Purchase #7	$48.96	9.199%	$53.4638	$53.46	$53.45	$53.50
7 purchase totals =	$857.45		$925.3594	$925.36	$925.35	$925.50