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	$196.54	7.278%	$210.8442	$210.84	$210.85	$210.80
Purchase #2	$111.30	7.307%	$119.4327	$119.43	$119.45	$119.40
Purchase #3	$216.71	5.109%	$227.7817	$227.78	$227.80	$227.80
Purchase #4	$107.98	7.568%	$116.1519	$116.15	$116.15	$116.20
Purchase #5	$58.75	6.841%	$62.7691	$62.77	$62.75	$62.80
Purchase #6	$22.87	13.162%	$25.8801	$25.88	$25.90	$25.90
Purchase #7	$70.47	11.475%	$78.5564	$78.56	$78.55	$78.60
7 purchase totals =	$784.62		$841.4161	$841.41	$841.45	$841.50