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	$168.26	10.849%	$186.5145	$186.51	$186.50	$186.50
Purchase #2	$225.33	12.427%	$253.3318	$253.33	$253.35	$253.30
Purchase #3	$169.96	11.495%	$189.4969	$189.50	$189.50	$189.50
Purchase #4	$92.49	7.611%	$99.5294	$99.53	$99.55	$99.50
Purchase #5	$70.79	8.467%	$76.7838	$76.78	$76.80	$76.80
Purchase #6	$112.74	12.566%	$126.9069	$126.91	$126.90	$126.90
Purchase #7	$65.60	8.458%	$71.1484	$71.15	$71.15	$71.10
7 purchase totals =	$905.17		$1,003.7117	$1,003.71	$1,003.75	$1,003.60