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	$193.95	9.664%	$212.6933	$212.69	$212.70	$212.70
Purchase #2	$31.42	3.333%	$32.4672	$32.47	$32.45	$32.50
Purchase #3	$206.90	4.700%	$216.6243	$216.62	$216.60	$216.60
Purchase #4	$235.69	6.231%	$250.3758	$250.38	$250.40	$250.40
Purchase #5	$81.47	13.376%	$92.3674	$92.37	$92.35	$92.40
Purchase #6	$139.62	4.194%	$145.4757	$145.48	$145.50	$145.50
Purchase #7	$214.46	12.632%	$241.5506	$241.55	$241.55	$241.60
7 purchase totals =	$1,103.51		$1,191.5543	$1,191.56	$1,191.55	$1,191.70