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	$80.73	7.113%	$86.4723	$86.47	$86.45	$86.50
Purchase #2	$99.30	7.153%	$106.4029	$106.40	$106.40	$106.40
Purchase #3	$73.56	8.170%	$79.5699	$79.57	$79.55	$79.60
Purchase #4	$148.51	3.369%	$153.5133	$153.51	$153.50	$153.50
Purchase #5	$121.47	4.834%	$127.3419	$127.34	$127.35	$127.30
Purchase #6	$112.73	13.519%	$127.97	$127.97	$127.95	$128.00
Purchase #7	$103.63	5.466%	$109.2944	$109.29	$109.30	$109.30
7 purchase totals =	$739.93		$790.5647	$790.55	$790.50	$790.60