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	$112.43	9.691%	$123.3256	$123.33	$123.35	$123.30
Purchase #2	$238.78	9.196%	$260.7382	$260.74	$260.75	$260.70
Purchase #3	$104.78	9.666%	$114.908	$114.91	$114.90	$114.90
Purchase #4	$90.92	8.302%	$98.4682	$98.47	$98.45	$98.50
Purchase #5	$64.75	10.218%	$71.3662	$71.37	$71.35	$71.40
Purchase #6	$60.57	11.487%	$67.5277	$67.53	$67.55	$67.50
Purchase #7	$73.70	11.818%	$82.4099	$82.41	$82.40	$82.40
7 purchase totals =	$745.93		$818.7438	$818.76	$818.75	$818.70