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	$102.94	6.846%	$109.9873	$109.99	$110.00	$110.00
Purchase #2	$175.97	13.366%	$199.4902	$199.49	$199.50	$199.50
Purchase #3	$11.49	12.128%	$12.8835	$12.88	$12.90	$12.90
Purchase #4	$68.86	3.811%	$71.4843	$71.48	$71.50	$71.50
Purchase #5	$92.76	7.179%	$99.4192	$99.42	$99.40	$99.40
Purchase #6	$234.33	12.235%	$263.0003	$263.00	$263.00	$263.00
Purchase #7	$225.42	13.629%	$256.1425	$256.14	$256.15	$256.10
7 purchase totals =	$911.77		$1,012.4073	$1,012.40	$1,012.45	$1,012.40