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	$152.89	9.322%	$167.1424	$167.14	$167.15	$167.10
Purchase #2	$78.57	7.465%	$84.4353	$84.44	$84.45	$84.40
Purchase #3	$95.94	5.192%	$100.9212	$100.92	$100.90	$100.90
Purchase #4	$47.98	11.191%	$53.3494	$53.35	$53.35	$53.30
Purchase #5	$38.44	10.455%	$42.4589	$42.46	$42.45	$42.50
Purchase #6	$118.91	7.399%	$127.7082	$127.71	$127.70	$127.70
Purchase #7	$121.50	6.236%	$129.0767	$129.08	$129.10	$129.10
7 purchase totals =	$654.23		$705.0921	$705.10	$705.10	$705.00