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	$148.71	11.305%	$165.5217	$165.52	$165.50	$165.50
Purchase #2	$131.47	12.661%	$148.1154	$148.12	$148.10	$148.10
Purchase #3	$34.75	10.675%	$38.4596	$38.46	$38.45	$38.50
Purchase #4	$84.64	9.109%	$92.3499	$92.35	$92.35	$92.30
Purchase #5	$96.90	5.623%	$102.3487	$102.35	$102.35	$102.30
Purchase #6	$126.67	9.761%	$139.0343	$139.03	$139.05	$139.00
Purchase #7	$229.92	9.404%	$251.5417	$251.54	$251.55	$251.50
7 purchase totals =	$853.06		$937.3713	$937.37	$937.35	$937.20