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	$248.74	9.176%	$271.5644	$271.56	$271.55	$271.60
Purchase #2	$183.79	13.806%	$209.164	$209.16	$209.15	$209.20
Purchase #3	$19.59	8.736%	$21.3014	$21.30	$21.30	$21.30
Purchase #4	$31.96	4.373%	$33.3576	$33.36	$33.35	$33.40
Purchase #5	$54.60	9.295%	$59.6751	$59.68	$59.70	$59.70
Purchase #6	$80.27	5.342%	$84.558	$84.56	$84.55	$84.60
Purchase #7	$232.77	9.824%	$255.6373	$255.64	$255.65	$255.60
7 purchase totals =	$851.72		$935.2578	$935.26	$935.25	$935.40