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	$36.77	3.155%	$37.9301	$37.93	$37.95	$37.90
Purchase #2	$53.84	6.470%	$57.3234	$57.32	$57.30	$57.30
Purchase #3	$182.25	3.262%	$188.195	$188.20	$188.20	$188.20
Purchase #4	$118.53	4.669%	$124.0642	$124.06	$124.05	$124.10
Purchase #5	$34.29	8.313%	$37.1405	$37.14	$37.15	$37.10
Purchase #6	$181.64	10.357%	$200.4525	$200.45	$200.45	$200.50
Purchase #7	$81.98	9.155%	$89.4853	$89.49	$89.50	$89.50
7 purchase totals =	$689.30		$734.5910	$734.59	$734.60	$734.60