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	$165.41	8.516%	$179.4963	$179.50	$179.50	$179.50
Purchase #2	$248.32	9.481%	$271.8632	$271.86	$271.85	$271.90
Purchase #3	$55.67	9.119%	$60.7465	$60.75	$60.75	$60.70
Purchase #4	$161.45	3.709%	$167.4382	$167.44	$167.45	$167.40
Purchase #5	$120.48	5.827%	$127.5004	$127.50	$127.50	$127.50
Purchase #6	$73.87	10.129%	$81.3523	$81.35	$81.35	$81.40
Purchase #7	$203.40	12.163%	$228.1395	$228.14	$228.15	$228.10
7 purchase totals =	$1,028.60		$1,116.5364	$1,116.54	$1,116.55	$1,116.50