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	$188.51	10.823%	$208.9124	$208.91	$208.90	$208.90
Purchase #2	$141.96	7.156%	$152.1187	$152.12	$152.10	$152.10
Purchase #3	$178.36	7.384%	$191.5301	$191.53	$191.55	$191.50
Purchase #4	$99.52	6.300%	$105.7898	$105.79	$105.80	$105.80
Purchase #5	$145.38	5.282%	$153.059	$153.06	$153.05	$153.10
Purchase #6	$112.85	10.396%	$124.5819	$124.58	$124.60	$124.60
Purchase #7	$145.45	11.585%	$162.3004	$162.30	$162.30	$162.30
7 purchase totals =	$1,012.03		$1,098.2923	$1,098.29	$1,098.30	$1,098.30