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	$179.26	10.649%	$198.3494	$198.35	$198.35	$198.30
Purchase #2	$5.60	12.770%	$6.3151	$6.32	$6.30	$6.30
Purchase #3	$95.89	4.269%	$99.9835	$99.98	$100.00	$100.00
Purchase #4	$27.75	5.470%	$29.2679	$29.27	$29.25	$29.30
Purchase #5	$244.53	4.739%	$256.1183	$256.12	$256.10	$256.10
Purchase #6	$49.59	12.666%	$55.8711	$55.87	$55.85	$55.90
Purchase #7	$56.31	9.267%	$61.5282	$61.53	$61.55	$61.50
7 purchase totals =	$658.93		$707.4335	$707.44	$707.40	$707.40