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	$192.54	10.858%	$213.446	$213.45	$213.45	$213.40
Purchase #2	$246.25	8.657%	$267.5679	$267.57	$267.55	$267.60
Purchase #3	$69.47	4.723%	$72.7511	$72.75	$72.75	$72.80
Purchase #4	$91.81	8.474%	$99.59	$99.59	$99.60	$99.60
Purchase #5	$78.56	4.670%	$82.2288	$82.23	$82.25	$82.20
Purchase #6	$153.36	13.655%	$174.3013	$174.30	$174.30	$174.30
Purchase #7	$35.76	6.395%	$38.0469	$38.05	$38.05	$38.00
7 purchase totals =	$867.75		$947.9320	$947.94	$947.95	$947.90