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	$82.36	4.638%	$86.1799	$86.18	$86.20	$86.20
Purchase #2	$213.73	6.614%	$227.8661	$227.87	$227.85	$227.90
Purchase #3	$216.56	12.712%	$244.0891	$244.09	$244.10	$244.10
Purchase #4	$115.38	7.200%	$123.6874	$123.69	$123.70	$123.70
Purchase #5	$56.36	13.285%	$63.8474	$63.85	$63.85	$63.80
Purchase #6	$72.72	7.848%	$78.4271	$78.43	$78.45	$78.40
Purchase #7	$204.74	3.524%	$211.955	$211.96	$211.95	$212.00
7 purchase totals =	$961.85		$1,036.0520	$1,036.07	$1,036.10	$1,036.10