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	$86.52	5.702%	$91.4534	$91.45	$91.45	$91.50
Purchase #2	$116.90	9.544%	$128.0569	$128.06	$128.05	$128.10
Purchase #3	$99.63	13.301%	$112.8818	$112.88	$112.90	$112.90
Purchase #4	$180.28	5.700%	$190.556	$190.56	$190.55	$190.60
Purchase #5	$211.36	8.228%	$228.7507	$228.75	$228.75	$228.80
Purchase #6	$220.82	3.828%	$229.273	$229.27	$229.25	$229.30
Purchase #7	$114.73	4.175%	$119.52	$119.52	$119.50	$119.50
7 purchase totals =	$1,030.24		$1,100.4918	$1,100.49	$1,100.45	$1,100.70