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	$68.96	4.408%	$71.9998	$72.00	$72.00	$72.00
Purchase #2	$136.49	10.235%	$150.4598	$150.46	$150.45	$150.50
Purchase #3	$194.60	12.517%	$218.9581	$218.96	$218.95	$219.00
Purchase #4	$229.40	6.328%	$243.9164	$243.92	$243.90	$243.90
Purchase #5	$52.84	12.752%	$59.5782	$59.58	$59.60	$59.60
Purchase #6	$127.41	4.151%	$132.6988	$132.70	$132.70	$132.70
Purchase #7	$105.36	10.368%	$116.2837	$116.28	$116.30	$116.30
7 purchase totals =	$915.06		$993.8948	$993.90	$993.90	$994.00