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	$213.62	4.630%	$223.5106	$223.51	$223.50	$223.50
Purchase #2	$196.52	5.705%	$207.7315	$207.73	$207.75	$207.70
Purchase #3	$67.28	6.103%	$71.3861	$71.39	$71.40	$71.40
Purchase #4	$89.64	4.588%	$93.7527	$93.75	$93.75	$93.80
Purchase #5	$86.51	5.614%	$91.3667	$91.37	$91.35	$91.40
Purchase #6	$19.49	13.184%	$22.0596	$22.06	$22.05	$22.10
Purchase #7	$27.62	3.521%	$28.5925	$28.59	$28.60	$28.60
7 purchase totals =	$700.68		$738.3997	$738.40	$738.40	$738.50