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	$157.39	11.685%	$175.781	$175.78	$175.80	$175.80
Purchase #2	$29.60	12.712%	$33.3628	$33.36	$33.35	$33.40
Purchase #3	$245.83	7.375%	$263.96	$263.96	$263.95	$264.00
Purchase #4	$60.31	8.213%	$65.2633	$65.26	$65.25	$65.30
Purchase #5	$9.96	3.684%	$10.3269	$10.33	$10.35	$10.30
Purchase #6	$117.66	8.231%	$127.3446	$127.34	$127.35	$127.30
Purchase #7	$162.71	9.642%	$178.3985	$178.40	$178.40	$178.40
7 purchase totals =	$783.46		$854.4371	$854.43	$854.45	$854.50