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	$73.38	7.410%	$78.8175	$78.82	$78.80	$78.80
Purchase #2	$75.90	9.470%	$83.0877	$83.09	$83.10	$83.10
Purchase #3	$81.41	13.577%	$92.463	$92.46	$92.45	$92.50
Purchase #4	$52.85	13.742%	$60.1126	$60.11	$60.10	$60.10
Purchase #5	$72.30	5.150%	$76.0235	$76.02	$76.00	$76.00
Purchase #6	$188.85	9.373%	$206.5509	$206.55	$206.55	$206.60
Purchase #7	$147.91	8.377%	$160.3004	$160.30	$160.30	$160.30
7 purchase totals =	$692.60		$757.3556	$757.35	$757.30	$757.40