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	$175.47	3.770%	$182.0852	$182.09	$182.10	$182.10
Purchase #2	$104.98	9.436%	$114.8859	$114.89	$114.90	$114.90
Purchase #3	$64.88	9.779%	$71.2246	$71.22	$71.20	$71.20
Purchase #4	$215.33	12.790%	$242.8707	$242.87	$242.85	$242.90
Purchase #5	$226.39	8.835%	$246.3916	$246.39	$246.40	$246.40
Purchase #6	$85.29	5.356%	$89.8581	$89.86	$89.85	$89.90
Purchase #7	$243.40	11.689%	$271.851	$271.85	$271.85	$271.90
7 purchase totals =	$1,115.74		$1,219.1671	$1,219.17	$1,219.15	$1,219.30