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	$145.72	6.701%	$155.4847	$155.48	$155.50	$155.50
Purchase #2	$191.45	7.475%	$205.7609	$205.76	$205.75	$205.80
Purchase #3	$222.85	3.372%	$230.3645	$230.36	$230.35	$230.40
Purchase #4	$150.30	11.506%	$167.5935	$167.59	$167.60	$167.60
Purchase #5	$11.91	4.434%	$12.4381	$12.44	$12.45	$12.40
Purchase #6	$148.27	10.155%	$163.3268	$163.33	$163.35	$163.30
Purchase #7	$156.38	5.596%	$165.131	$165.13	$165.15	$165.10
7 purchase totals =	$1,026.88		$1,100.0995	$1,100.09	$1,100.15	$1,100.10