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	$144.51	6.755%	$154.2717	$154.27	$154.25	$154.30
Purchase #2	$51.54	7.500%	$55.4055	$55.41	$55.40	$55.40
Purchase #3	$79.78	6.615%	$85.0574	$85.06	$85.05	$85.10
Purchase #4	$87.51	8.390%	$94.8521	$94.85	$94.85	$94.90
Purchase #5	$94.81	6.250%	$100.7356	$100.74	$100.75	$100.70
Purchase #6	$159.43	6.141%	$169.2206	$169.22	$169.20	$169.20
Purchase #7	$67.93	8.803%	$73.9099	$73.91	$73.90	$73.90
7 purchase totals =	$685.51		$733.4528	$733.46	$733.40	$733.50