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	$119.69	8.668%	$130.0647	$130.06	$130.05	$130.10
Purchase #2	$119.50	3.667%	$123.8821	$123.88	$123.90	$123.90
Purchase #3	$213.53	11.500%	$238.086	$238.09	$238.10	$238.10
Purchase #4	$205.57	9.564%	$225.2307	$225.23	$225.25	$225.20
Purchase #5	$52.72	6.469%	$56.1305	$56.13	$56.15	$56.10
Purchase #6	$147.71	5.786%	$156.2565	$156.26	$156.25	$156.30
Purchase #7	$121.38	12.319%	$136.3328	$136.33	$136.35	$136.30
7 purchase totals =	$980.10		$1,065.9833	$1,065.98	$1,066.05	$1,066.00