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	$98.35	9.278%	$107.4749	$107.47	$107.45	$107.50
Purchase #2	$200.98	5.154%	$211.3385	$211.34	$211.35	$211.30
Purchase #3	$48.83	12.327%	$54.8493	$54.85	$54.85	$54.80
Purchase #4	$150.73	3.805%	$156.4653	$156.47	$156.45	$156.50
Purchase #5	$98.87	10.528%	$109.279	$109.28	$109.30	$109.30
Purchase #6	$163.91	4.485%	$171.2614	$171.26	$171.25	$171.30
Purchase #7	$150.96	7.845%	$162.8028	$162.80	$162.80	$162.80
7 purchase totals =	$912.63		$973.4712	$973.47	$973.45	$973.50