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	$179.43	9.171%	$195.8855	$195.89	$195.90	$195.90
Purchase #2	$40.58	3.837%	$42.1371	$42.14	$42.15	$42.10
Purchase #3	$143.38	3.317%	$148.1359	$148.14	$148.15	$148.10
Purchase #4	$129.41	9.233%	$141.3584	$141.36	$141.35	$141.40
Purchase #5	$99.84	4.172%	$104.0053	$104.01	$104.00	$104.00
Purchase #6	$181.27	8.452%	$196.5909	$196.59	$196.60	$196.60
Purchase #7	$148.38	3.322%	$153.3092	$153.31	$153.30	$153.30
7 purchase totals =	$922.29		$981.4223	$981.44	$981.45	$981.40