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	$171.69	13.487%	$194.8458	$194.85	$194.85	$194.80
Purchase #2	$245.41	9.719%	$269.2614	$269.26	$269.25	$269.30
Purchase #3	$239.33	11.809%	$267.5925	$267.59	$267.60	$267.60
Purchase #4	$24.33	6.718%	$25.9645	$25.96	$25.95	$26.00
Purchase #5	$164.89	6.423%	$175.4809	$175.48	$175.50	$175.50
Purchase #6	$38.36	6.318%	$40.7836	$40.78	$40.80	$40.80
Purchase #7	$35.54	13.421%	$40.3098	$40.31	$40.30	$40.30
7 purchase totals =	$919.55		$1,014.2385	$1,014.23	$1,014.25	$1,014.30