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	$160.65	4.726%	$168.2423	$168.24	$168.25	$168.20
Purchase #2	$93.43	11.588%	$104.2567	$104.26	$104.25	$104.30
Purchase #3	$241.71	4.840%	$253.4088	$253.41	$253.40	$253.40
Purchase #4	$13.87	10.152%	$15.2781	$15.28	$15.30	$15.30
Purchase #5	$112.29	10.630%	$124.2264	$124.23	$124.25	$124.20
Purchase #6	$28.49	10.423%	$31.4595	$31.46	$31.45	$31.50
Purchase #7	$57.83	10.424%	$63.8582	$63.86	$63.85	$63.90
7 purchase totals =	$708.27		$760.7300	$760.74	$760.75	$760.80