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	$49.86	8.283%	$53.9899	$53.99	$54.00	$54.00
Purchase #2	$242.86	11.818%	$271.5612	$271.56	$271.55	$271.60
Purchase #3	$94.59	4.839%	$99.1672	$99.17	$99.15	$99.20
Purchase #4	$167.89	8.761%	$182.5988	$182.60	$182.60	$182.60
Purchase #5	$209.71	11.127%	$233.0444	$233.04	$233.05	$233.00
Purchase #6	$37.43	12.866%	$42.2457	$42.25	$42.25	$42.20
Purchase #7	$200.93	9.866%	$220.7538	$220.75	$220.75	$220.80
7 purchase totals =	$1,003.27		$1,103.3610	$1,103.36	$1,103.35	$1,103.40