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	$140.76	3.266%	$145.3572	$145.36	$145.35	$145.40
Purchase #2	$104.59	6.798%	$111.7	$111.70	$111.70	$111.70
Purchase #3	$11.93	3.874%	$12.3922	$12.39	$12.40	$12.40
Purchase #4	$188.43	7.345%	$202.2702	$202.27	$202.25	$202.30
Purchase #5	$63.34	6.163%	$67.2436	$67.24	$67.25	$67.20
Purchase #6	$160.66	13.492%	$182.3362	$182.34	$182.35	$182.30
Purchase #7	$80.33	6.841%	$85.8254	$85.83	$85.85	$85.80
7 purchase totals =	$750.04		$807.1248	$807.13	$807.15	$807.10