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	$174.63	5.633%	$184.4669	$184.47	$184.45	$184.50
Purchase #2	$220.31	8.265%	$238.5186	$238.52	$238.50	$238.50
Purchase #3	$244.71	4.305%	$255.2448	$255.24	$255.25	$255.20
Purchase #4	$29.58	6.245%	$31.4273	$31.43	$31.45	$31.40
Purchase #5	$115.51	9.874%	$126.9155	$126.92	$126.90	$126.90
Purchase #6	$60.41	6.299%	$64.2152	$64.22	$64.20	$64.20
Purchase #7	$234.98	6.606%	$250.5028	$250.50	$250.50	$250.50
7 purchase totals =	$1,080.13		$1,151.2911	$1,151.30	$1,151.25	$1,151.20