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	$215.44	13.219%	$243.919	$243.92	$243.90	$243.90
Purchase #2	$125.81	4.824%	$131.8791	$131.88	$131.90	$131.90
Purchase #3	$52.86	11.215%	$58.7882	$58.79	$58.80	$58.80
Purchase #4	$134.90	12.792%	$152.1564	$152.16	$152.15	$152.20
Purchase #5	$226.29	7.823%	$243.9927	$243.99	$244.00	$244.00
Purchase #6	$150.67	5.384%	$158.7821	$158.78	$158.80	$158.80
Purchase #7	$124.79	3.303%	$128.9118	$128.91	$128.90	$128.90
7 purchase totals =	$1,030.76		$1,118.4293	$1,118.43	$1,118.45	$1,118.50