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	$223.59	6.437%	$237.9825	$237.98	$238.00	$238.00
Purchase #2	$171.44	6.221%	$182.1053	$182.11	$182.10	$182.10
Purchase #3	$129.49	8.177%	$140.0784	$140.08	$140.10	$140.10
Purchase #4	$146.71	6.402%	$156.1024	$156.10	$156.10	$156.10
Purchase #5	$172.70	9.407%	$188.9459	$188.95	$188.95	$188.90
Purchase #6	$83.77	10.411%	$92.4913	$92.49	$92.50	$92.50
Purchase #7	$50.43	6.287%	$53.6005	$53.60	$53.60	$53.60
7 purchase totals =	$978.13		$1,051.3063	$1,051.31	$1,051.35	$1,051.30