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	$53.54	7.732%	$57.6797	$57.68	$57.70	$57.70
Purchase #2	$67.33	7.376%	$72.2963	$72.30	$72.30	$72.30
Purchase #3	$29.64	3.199%	$30.5882	$30.59	$30.60	$30.60
Purchase #4	$104.78	10.141%	$115.4057	$115.41	$115.40	$115.40
Purchase #5	$52.86	3.809%	$54.8734	$54.87	$54.85	$54.90
Purchase #6	$181.68	3.207%	$187.5065	$187.51	$187.50	$187.50
Purchase #7	$200.74	12.341%	$225.5133	$225.51	$225.50	$225.50
7 purchase totals =	$690.57		$743.8631	$743.87	$743.85	$743.90