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	$179.90	4.748%	$188.4417	$188.44	$188.45	$188.40
Purchase #2	$131.83	8.804%	$143.4363	$143.44	$143.45	$143.40
Purchase #3	$51.43	3.486%	$53.2228	$53.22	$53.20	$53.20
Purchase #4	$244.43	5.825%	$258.668	$258.67	$258.65	$258.70
Purchase #5	$44.69	6.107%	$47.4192	$47.42	$47.40	$47.40
Purchase #6	$211.37	12.844%	$238.5184	$238.52	$238.50	$238.50
Purchase #7	$66.78	9.631%	$73.2116	$73.21	$73.20	$73.20
7 purchase totals =	$930.43		$1,002.9180	$1,002.92	$1,002.85	$1,002.80