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	$151.83	5.216%	$159.7495	$159.75	$159.75	$159.70
Purchase #2	$19.61	11.126%	$21.7918	$21.79	$21.80	$21.80
Purchase #3	$168.75	9.716%	$185.1458	$185.15	$185.15	$185.10
Purchase #4	$70.81	12.435%	$79.6152	$79.62	$79.60	$79.60
Purchase #5	$72.34	6.856%	$77.2996	$77.30	$77.30	$77.30
Purchase #6	$80.72	13.194%	$91.3702	$91.37	$91.35	$91.40
Purchase #7	$126.92	3.537%	$131.4092	$131.41	$131.40	$131.40
7 purchase totals =	$690.98		$746.3813	$746.39	$746.35	$746.30