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	$110.70	7.751%	$119.2804	$119.28	$119.30	$119.30
Purchase #2	$70.84	4.845%	$74.2722	$74.27	$74.25	$74.30
Purchase #3	$69.36	13.797%	$78.9296	$78.93	$78.95	$78.90
Purchase #4	$212.73	4.443%	$222.1816	$222.18	$222.20	$222.20
Purchase #5	$247.72	4.400%	$258.6197	$258.62	$258.60	$258.60
Purchase #6	$222.71	3.492%	$230.487	$230.49	$230.50	$230.50
Purchase #7	$54.36	5.780%	$57.502	$57.50	$57.50	$57.50
7 purchase totals =	$988.42		$1,041.2725	$1,041.27	$1,041.30	$1,041.30