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	$160.31	5.579%	$169.2537	$169.25	$169.25	$169.30
Purchase #2	$213.28	12.254%	$239.4153	$239.42	$239.40	$239.40
Purchase #3	$9.69	6.600%	$10.3295	$10.33	$10.35	$10.30
Purchase #4	$221.61	6.314%	$235.6025	$235.60	$235.60	$235.60
Purchase #5	$205.47	5.411%	$216.588	$216.59	$216.60	$216.60
Purchase #6	$19.87	10.166%	$21.89	$21.89	$21.90	$21.90
Purchase #7	$31.32	6.375%	$33.3167	$33.32	$33.30	$33.30
7 purchase totals =	$861.55		$926.3957	$926.40	$926.40	$926.40