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	$94.49	10.850%	$104.7422	$104.74	$104.75	$104.70
Purchase #2	$114.48	5.231%	$120.4684	$120.47	$120.45	$120.50
Purchase #3	$101.86	12.225%	$114.3124	$114.31	$114.30	$114.30
Purchase #4	$139.91	10.712%	$154.8972	$154.90	$154.90	$154.90
Purchase #5	$216.74	3.216%	$223.7104	$223.71	$223.70	$223.70
Purchase #6	$104.82	4.552%	$109.5914	$109.59	$109.60	$109.60
Purchase #7	$83.61	3.417%	$86.467	$86.47	$86.45	$86.50
7 purchase totals =	$855.91		$914.1890	$914.19	$914.15	$914.20