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	$174.71	8.412%	$189.4066	$189.41	$189.40	$189.40
Purchase #2	$50.97	9.603%	$55.8646	$55.86	$55.85	$55.90
Purchase #3	$163.70	6.520%	$174.3732	$174.37	$174.35	$174.40
Purchase #4	$46.82	9.277%	$51.1635	$51.16	$51.15	$51.20
Purchase #5	$189.59	13.483%	$215.1524	$215.15	$215.15	$215.20
Purchase #6	$211.25	5.114%	$222.0533	$222.05	$222.05	$222.10
Purchase #7	$215.51	9.220%	$235.38	$235.38	$235.40	$235.40
7 purchase totals =	$1,052.55		$1,143.3936	$1,143.38	$1,143.35	$1,143.60