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	$28.67	4.190%	$29.8713	$29.87	$29.85	$29.90
Purchase #2	$51.85	6.470%	$55.2047	$55.20	$55.20	$55.20
Purchase #3	$114.48	13.745%	$130.2153	$130.22	$130.20	$130.20
Purchase #4	$153.82	5.834%	$162.7939	$162.79	$162.80	$162.80
Purchase #5	$56.92	4.420%	$59.4359	$59.44	$59.45	$59.40
Purchase #6	$31.98	4.754%	$33.5003	$33.50	$33.50	$33.50
Purchase #7	$243.92	6.284%	$259.2479	$259.25	$259.25	$259.20
7 purchase totals =	$681.64		$730.2693	$730.27	$730.25	$730.20