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	$195.75	3.364%	$202.335	$202.34	$202.35	$202.30
Purchase #2	$148.92	9.296%	$162.7636	$162.76	$162.75	$162.80
Purchase #3	$80.83	10.708%	$89.4853	$89.49	$89.50	$89.50
Purchase #4	$184.93	3.363%	$191.1492	$191.15	$191.15	$191.10
Purchase #5	$227.98	11.540%	$254.2889	$254.29	$254.30	$254.30
Purchase #6	$55.41	6.103%	$58.7917	$58.79	$58.80	$58.80
Purchase #7	$223.98	7.725%	$241.2825	$241.28	$241.30	$241.30
7 purchase totals =	$1,117.80		$1,200.0962	$1,200.10	$1,200.15	$1,200.10