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	$174.38	6.466%	$185.6554	$185.66	$185.65	$185.70
Purchase #2	$32.30	3.264%	$33.3543	$33.35	$33.35	$33.40
Purchase #3	$101.63	3.467%	$105.1535	$105.15	$105.15	$105.20
Purchase #4	$73.48	12.357%	$82.5599	$82.56	$82.55	$82.60
Purchase #5	$231.73	13.525%	$263.0715	$263.07	$263.05	$263.10
Purchase #6	$52.45	4.280%	$54.6949	$54.69	$54.70	$54.70
Purchase #7	$169.26	13.689%	$192.43	$192.43	$192.45	$192.40
7 purchase totals =	$835.23		$916.9195	$916.91	$916.90	$917.10