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	$218.72	4.369%	$228.2759	$228.28	$228.30	$228.30
Purchase #2	$134.74	9.190%	$147.1226	$147.12	$147.10	$147.10
Purchase #3	$100.66	13.381%	$114.1293	$114.13	$114.15	$114.10
Purchase #4	$86.89	4.397%	$90.7106	$90.71	$90.70	$90.70
Purchase #5	$103.81	6.102%	$110.1445	$110.14	$110.15	$110.10
Purchase #6	$250.43	12.125%	$280.7946	$280.79	$280.80	$280.80
Purchase #7	$199.88	10.689%	$221.2452	$221.25	$221.25	$221.20
7 purchase totals =	$1,095.13		$1,192.4227	$1,192.42	$1,192.45	$1,192.30