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	$173.43	8.719%	$188.5514	$188.55	$188.55	$188.60
Purchase #2	$52.73	5.188%	$55.4656	$55.47	$55.45	$55.50
Purchase #3	$248.37	11.135%	$276.026	$276.03	$276.05	$276.00
Purchase #4	$120.28	5.401%	$126.7763	$126.78	$126.80	$126.80
Purchase #5	$27.79	13.251%	$31.4725	$31.47	$31.45	$31.50
Purchase #6	$57.79	13.723%	$65.7205	$65.72	$65.70	$65.70
Purchase #7	$105.39	4.217%	$109.8343	$109.83	$109.85	$109.80
7 purchase totals =	$785.78		$853.8466	$853.85	$853.85	$853.90