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	$141.45	12.737%	$159.4665	$159.47	$159.45	$159.50
Purchase #2	$138.46	11.254%	$154.0423	$154.04	$154.05	$154.00
Purchase #3	$233.87	10.366%	$258.113	$258.11	$258.10	$258.10
Purchase #4	$79.76	13.237%	$90.3178	$90.32	$90.30	$90.30
Purchase #5	$73.56	6.302%	$78.1958	$78.20	$78.20	$78.20
Purchase #6	$184.33	5.237%	$193.9834	$193.98	$194.00	$194.00
Purchase #7	$155.39	4.486%	$162.3608	$162.36	$162.35	$162.40
7 purchase totals =	$1,006.82		$1,096.4796	$1,096.48	$1,096.45	$1,096.50