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	$69.54	4.140%	$72.419	$72.42	$72.40	$72.40
Purchase #2	$110.69	4.815%	$116.0197	$116.02	$116.00	$116.00
Purchase #3	$123.58	3.414%	$127.799	$127.80	$127.80	$127.80
Purchase #4	$191.64	12.316%	$215.2424	$215.24	$215.25	$215.20
Purchase #5	$109.89	7.617%	$118.2603	$118.26	$118.25	$118.30
Purchase #6	$188.78	8.290%	$204.4299	$204.43	$204.45	$204.40
Purchase #7	$44.36	4.259%	$46.2493	$46.25	$46.25	$46.20
7 purchase totals =	$838.48		$900.4196	$900.42	$900.40	$900.30