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	$202.29	9.533%	$221.5743	$221.57	$221.55	$221.60
Purchase #2	$200.63	3.429%	$207.5096	$207.51	$207.50	$207.50
Purchase #3	$180.58	8.705%	$196.2995	$196.30	$196.30	$196.30
Purchase #4	$79.91	13.192%	$90.4517	$90.45	$90.45	$90.50
Purchase #5	$49.38	8.658%	$53.6553	$53.66	$53.65	$53.70
Purchase #6	$180.59	5.780%	$191.0281	$191.03	$191.05	$191.00
Purchase #7	$249.77	5.325%	$263.0703	$263.07	$263.05	$263.10
7 purchase totals =	$1,143.15		$1,223.5888	$1,223.59	$1,223.55	$1,223.70