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	$53.27	11.408%	$59.347	$59.35	$59.35	$59.30
Purchase #2	$162.90	7.685%	$175.4189	$175.42	$175.40	$175.40
Purchase #3	$186.96	7.437%	$200.8642	$200.86	$200.85	$200.90
Purchase #4	$132.74	9.481%	$145.3251	$145.33	$145.35	$145.30
Purchase #5	$200.69	11.253%	$223.2736	$223.27	$223.25	$223.30
Purchase #6	$110.84	7.464%	$119.1131	$119.11	$119.10	$119.10
Purchase #7	$118.97	12.539%	$133.8876	$133.89	$133.90	$133.90
7 purchase totals =	$966.37		$1,057.2295	$1,057.23	$1,057.20	$1,057.20