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	$59.47	6.675%	$63.4396	$63.44	$63.45	$63.40
Purchase #2	$179.28	9.539%	$196.3815	$196.38	$196.40	$196.40
Purchase #3	$114.50	7.648%	$123.257	$123.26	$123.25	$123.30
Purchase #4	$79.29	5.781%	$83.8738	$83.87	$83.85	$83.90
Purchase #5	$70.74	5.624%	$74.7184	$74.72	$74.70	$74.70
Purchase #6	$236.32	9.705%	$259.2549	$259.25	$259.25	$259.30
Purchase #7	$89.86	9.180%	$98.1091	$98.11	$98.10	$98.10
7 purchase totals =	$829.46		$899.0343	$899.03	$899.00	$899.10