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	$86.60	9.832%	$95.1145	$95.11	$95.10	$95.10
Purchase #2	$92.87	9.138%	$101.3565	$101.36	$101.35	$101.40
Purchase #3	$104.54	4.279%	$109.0133	$109.01	$109.00	$109.00
Purchase #4	$245.50	11.568%	$273.8994	$273.90	$273.90	$273.90
Purchase #5	$105.62	3.389%	$109.1995	$109.20	$109.20	$109.20
Purchase #6	$244.97	10.368%	$270.3685	$270.37	$270.35	$270.40
Purchase #7	$54.87	7.832%	$59.1674	$59.17	$59.15	$59.20
7 purchase totals =	$934.97		$1,018.1191	$1,018.12	$1,018.05	$1,018.20