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	$86.27	5.113%	$90.681	$90.68	$90.70	$90.70
Purchase #2	$53.26	12.322%	$59.8227	$59.82	$59.80	$59.80
Purchase #3	$143.84	9.776%	$157.9018	$157.90	$157.90	$157.90
Purchase #4	$152.80	12.507%	$171.9107	$171.91	$171.90	$171.90
Purchase #5	$154.73	4.280%	$161.3524	$161.35	$161.35	$161.40
Purchase #6	$194.53	3.182%	$200.7199	$200.72	$200.70	$200.70
Purchase #7	$80.79	9.592%	$88.5394	$88.54	$88.55	$88.50
7 purchase totals =	$866.22		$930.9279	$930.92	$930.90	$930.90