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	$144.70	5.673%	$152.9088	$152.91	$152.90	$152.90
Purchase #2	$169.96	6.840%	$181.5853	$181.59	$181.60	$181.60
Purchase #3	$172.95	9.747%	$189.8074	$189.81	$189.80	$189.80
Purchase #4	$120.84	3.320%	$124.8519	$124.85	$124.85	$124.90
Purchase #5	$59.98	9.139%	$65.4616	$65.46	$65.45	$65.50
Purchase #6	$73.92	13.524%	$83.9169	$83.92	$83.90	$83.90
Purchase #7	$96.82	3.489%	$100.198	$100.20	$100.20	$100.20
7 purchase totals =	$839.17		$898.7299	$898.74	$898.70	$898.80