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	$218.40	4.538%	$228.311	$228.31	$228.30	$228.30
Purchase #2	$55.94	11.586%	$62.4212	$62.42	$62.40	$62.40
Purchase #3	$249.30	13.217%	$282.25	$282.25	$282.25	$282.30
Purchase #4	$133.34	5.109%	$140.1523	$140.15	$140.15	$140.20
Purchase #5	$127.76	13.712%	$145.2785	$145.28	$145.30	$145.30
Purchase #6	$120.97	6.305%	$128.5972	$128.60	$128.60	$128.60
Purchase #7	$247.59	4.547%	$258.8479	$258.85	$258.85	$258.80
7 purchase totals =	$1,153.30		$1,245.8581	$1,245.86	$1,245.85	$1,245.90