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	$184.66	8.764%	$200.8436	$200.84	$200.85	$200.80
Purchase #2	$55.80	4.663%	$58.402	$58.40	$58.40	$58.40
Purchase #3	$39.36	3.749%	$40.8356	$40.84	$40.85	$40.80
Purchase #4	$104.97	3.524%	$108.6691	$108.67	$108.65	$108.70
Purchase #5	$51.29	10.773%	$56.8155	$56.82	$56.80	$56.80
Purchase #6	$245.84	5.547%	$259.4767	$259.48	$259.50	$259.50
Purchase #7	$56.42	5.347%	$59.4368	$59.44	$59.45	$59.40
7 purchase totals =	$738.34		$784.4793	$784.49	$784.50	$784.40