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	$205.57	8.836%	$223.7342	$223.73	$223.75	$223.70
Purchase #2	$62.46	8.735%	$67.9159	$67.92	$67.90	$67.90
Purchase #3	$84.46	7.305%	$90.6298	$90.63	$90.65	$90.60
Purchase #4	$153.66	3.588%	$159.1733	$159.17	$159.15	$159.20
Purchase #5	$153.30	11.859%	$171.4798	$171.48	$171.50	$171.50
Purchase #6	$189.33	11.560%	$211.2165	$211.22	$211.20	$211.20
Purchase #7	$175.29	5.498%	$184.9274	$184.93	$184.95	$184.90
7 purchase totals =	$1,024.07		$1,109.0769	$1,109.08	$1,109.10	$1,109.00