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	$83.26	9.213%	$90.9307	$90.93	$90.95	$90.90
Purchase #2	$91.41	5.516%	$96.4522	$96.45	$96.45	$96.50
Purchase #3	$17.62	12.415%	$19.8075	$19.81	$19.80	$19.80
Purchase #4	$55.86	3.404%	$57.7615	$57.76	$57.75	$57.80
Purchase #5	$159.37	6.693%	$170.0366	$170.04	$170.05	$170.00
Purchase #6	$190.93	9.753%	$209.5514	$209.55	$209.55	$209.60
Purchase #7	$95.35	5.419%	$100.517	$100.52	$100.50	$100.50
7 purchase totals =	$693.80		$745.0569	$745.06	$745.05	$745.10