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	$173.83	3.581%	$180.0549	$180.05	$180.05	$180.10
Purchase #2	$19.48	4.587%	$20.3735	$20.37	$20.35	$20.40
Purchase #3	$37.76	6.830%	$40.339	$40.34	$40.35	$40.30
Purchase #4	$167.92	10.358%	$185.3132	$185.31	$185.30	$185.30
Purchase #5	$98.99	11.691%	$110.5629	$110.56	$110.55	$110.60
Purchase #6	$150.31	9.510%	$164.6045	$164.60	$164.60	$164.60
Purchase #7	$224.47	5.519%	$236.8585	$236.86	$236.85	$236.90
7 purchase totals =	$872.76		$938.1065	$938.09	$938.05	$938.20