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	$10.46	9.870%	$11.4924	$11.49	$11.50	$11.50
Purchase #2	$57.31	13.614%	$65.1122	$65.11	$65.10	$65.10
Purchase #3	$162.93	13.560%	$185.0233	$185.02	$185.00	$185.00
Purchase #4	$236.53	5.521%	$249.5888	$249.59	$249.60	$249.60
Purchase #5	$88.37	7.520%	$95.0154	$95.02	$95.00	$95.00
Purchase #6	$99.45	4.687%	$104.1112	$104.11	$104.10	$104.10
Purchase #7	$77.45	12.190%	$86.8912	$86.89	$86.90	$86.90
7 purchase totals =	$732.50		$797.2345	$797.23	$797.20	$797.20