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	$159.51	11.504%	$177.86	$177.86	$177.85	$177.90
Purchase #2	$125.49	6.393%	$133.5126	$133.51	$133.50	$133.50
Purchase #3	$181.64	13.732%	$206.5828	$206.58	$206.60	$206.60
Purchase #4	$147.86	12.872%	$166.8925	$166.89	$166.90	$166.90
Purchase #5	$224.94	11.356%	$250.4842	$250.48	$250.50	$250.50
Purchase #6	$90.55	9.748%	$99.3768	$99.38	$99.40	$99.40
Purchase #7	$9.83	11.154%	$10.9264	$10.93	$10.95	$10.90
7 purchase totals =	$939.82		$1,045.6353	$1,045.63	$1,045.70	$1,045.70