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	$118.39	4.220%	$123.3861	$123.39	$123.40	$123.40
Purchase #2	$155.86	6.541%	$166.0548	$166.05	$166.05	$166.10
Purchase #3	$47.36	4.617%	$49.5466	$49.55	$49.55	$49.50
Purchase #4	$112.30	13.377%	$127.3224	$127.32	$127.30	$127.30
Purchase #5	$15.70	11.564%	$17.5155	$17.52	$17.50	$17.50
Purchase #6	$98.36	8.280%	$106.5042	$106.50	$106.50	$106.50
Purchase #7	$111.82	12.791%	$126.1229	$126.12	$126.10	$126.10
7 purchase totals =	$659.79		$716.4525	$716.45	$716.40	$716.40