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	$40.97	5.602%	$43.2651	$43.27	$43.25	$43.30
Purchase #2	$216.91	12.486%	$243.9934	$243.99	$244.00	$244.00
Purchase #3	$91.69	11.641%	$102.3636	$102.36	$102.35	$102.40
Purchase #4	$64.56	4.406%	$67.4045	$67.40	$67.40	$67.40
Purchase #5	$32.45	13.362%	$36.786	$36.79	$36.80	$36.80
Purchase #6	$94.34	6.416%	$100.3929	$100.39	$100.40	$100.40
Purchase #7	$150.97	10.354%	$166.6014	$166.60	$166.60	$166.60
7 purchase totals =	$691.89		$760.8069	$760.80	$760.80	$760.90