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	$157.75	13.754%	$179.4469	$179.45	$179.45	$179.40
Purchase #2	$104.84	9.809%	$115.1238	$115.12	$115.10	$115.10
Purchase #3	$218.61	11.756%	$244.3098	$244.31	$244.30	$244.30
Purchase #4	$40.43	12.384%	$45.4369	$45.44	$45.45	$45.40
Purchase #5	$27.63	13.508%	$31.3623	$31.36	$31.35	$31.40
Purchase #6	$177.48	12.841%	$200.2702	$200.27	$200.25	$200.30
Purchase #7	$137.26	11.303%	$152.7745	$152.77	$152.75	$152.80
7 purchase totals =	$864.00		$968.7244	$968.72	$968.65	$968.70