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	$133.95	10.746%	$148.3443	$148.34	$148.35	$148.30
Purchase #2	$115.54	10.666%	$127.8635	$127.86	$127.85	$127.90
Purchase #3	$225.71	13.121%	$255.3254	$255.33	$255.35	$255.30
Purchase #4	$202.39	12.773%	$228.2413	$228.24	$228.25	$228.20
Purchase #5	$66.90	9.216%	$73.0655	$73.07	$73.05	$73.10
Purchase #6	$219.32	9.708%	$240.6116	$240.61	$240.60	$240.60
Purchase #7	$113.46	11.207%	$126.1755	$126.18	$126.20	$126.20
7 purchase totals =	$1,077.27		$1,199.6271	$1,199.63	$1,199.65	$1,199.60