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	$172.82	8.343%	$187.2384	$187.24	$187.25	$187.20
Purchase #2	$174.54	12.299%	$196.0067	$196.01	$196.00	$196.00
Purchase #3	$128.66	11.385%	$143.3079	$143.31	$143.30	$143.30
Purchase #4	$141.58	9.720%	$155.3416	$155.34	$155.35	$155.30
Purchase #5	$135.74	7.640%	$146.1105	$146.11	$146.10	$146.10
Purchase #6	$47.92	12.475%	$53.898	$53.90	$53.90	$53.90
Purchase #7	$12.89	11.849%	$14.4173	$14.42	$14.40	$14.40
7 purchase totals =	$814.15		$896.3204	$896.33	$896.30	$896.20