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	$127.81	4.556%	$133.633	$133.63	$133.65	$133.60
Purchase #2	$115.27	7.345%	$123.7366	$123.74	$123.75	$123.70
Purchase #3	$186.87	11.320%	$208.0237	$208.02	$208.00	$208.00
Purchase #4	$190.92	10.233%	$210.4568	$210.46	$210.45	$210.50
Purchase #5	$103.98	6.307%	$110.538	$110.54	$110.55	$110.50
Purchase #6	$181.62	9.236%	$198.3944	$198.39	$198.40	$198.40
Purchase #7	$81.31	10.577%	$89.9102	$89.91	$89.90	$89.90
7 purchase totals =	$987.78		$1,074.6927	$1,074.69	$1,074.70	$1,074.60