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	$93.76	10.457%	$103.5645	$103.56	$103.55	$103.60
Purchase #2	$38.68	10.492%	$42.7383	$42.74	$42.75	$42.70
Purchase #3	$168.80	7.543%	$181.5326	$181.53	$181.55	$181.50
Purchase #4	$68.99	3.548%	$71.4378	$71.44	$71.45	$71.40
Purchase #5	$130.60	7.403%	$140.2683	$140.27	$140.25	$140.30
Purchase #6	$144.52	12.244%	$162.215	$162.22	$162.20	$162.20
Purchase #7	$100.72	8.395%	$109.1754	$109.18	$109.20	$109.20
7 purchase totals =	$746.07		$810.9319	$810.94	$810.95	$810.90