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	$171.98	11.826%	$192.3184	$192.32	$192.30	$192.30
Purchase #2	$105.26	10.431%	$116.2397	$116.24	$116.25	$116.20
Purchase #3	$163.30	13.703%	$185.677	$185.68	$185.70	$185.70
Purchase #4	$217.76	12.183%	$244.2897	$244.29	$244.30	$244.30
Purchase #5	$171.99	4.587%	$179.8792	$179.88	$179.90	$179.90
Purchase #6	$185.46	6.111%	$196.7935	$196.79	$196.80	$196.80
Purchase #7	$71.60	10.718%	$79.2741	$79.27	$79.25	$79.30
7 purchase totals =	$1,087.35		$1,194.4716	$1,194.47	$1,194.50	$1,194.50