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	$86.65	3.556%	$89.7313	$89.73	$89.75	$89.70
Purchase #2	$237.38	7.127%	$254.2981	$254.30	$254.30	$254.30
Purchase #3	$135.74	11.276%	$151.046	$151.05	$151.05	$151.00
Purchase #4	$9.89	9.517%	$10.8312	$10.83	$10.85	$10.80
Purchase #5	$48.68	8.539%	$52.8368	$52.84	$52.85	$52.80
Purchase #6	$246.31	13.598%	$279.8032	$279.80	$279.80	$279.80
Purchase #7	$248.90	8.630%	$270.3801	$270.38	$270.40	$270.40
7 purchase totals =	$1,013.55		$1,108.9267	$1,108.93	$1,109.00	$1,108.80