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	$99.92	11.309%	$111.22	$111.22	$111.20	$111.20
Purchase #2	$68.50	6.732%	$73.1114	$73.11	$73.10	$73.10
Purchase #3	$198.50	8.574%	$215.5194	$215.52	$215.50	$215.50
Purchase #4	$63.67	12.846%	$71.849	$71.85	$71.85	$71.80
Purchase #5	$67.28	3.402%	$69.5689	$69.57	$69.55	$69.60
Purchase #6	$116.41	6.146%	$123.5646	$123.56	$123.55	$123.60
Purchase #7	$108.78	5.295%	$114.5399	$114.54	$114.55	$114.50
7 purchase totals =	$723.06		$779.3732	$779.37	$779.30	$779.30