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	$48.27	8.840%	$52.5371	$52.54	$52.55	$52.50
Purchase #2	$39.90	5.279%	$42.0063	$42.01	$42.00	$42.00
Purchase #3	$89.98	13.782%	$102.381	$102.38	$102.40	$102.40
Purchase #4	$194.54	8.351%	$210.786	$210.79	$210.80	$210.80
Purchase #5	$174.78	3.401%	$180.7243	$180.72	$180.70	$180.70
Purchase #6	$224.97	11.374%	$250.5581	$250.56	$250.55	$250.60
Purchase #7	$238.84	9.855%	$262.3777	$262.38	$262.40	$262.40
7 purchase totals =	$1,011.28		$1,101.3705	$1,101.38	$1,101.40	$1,101.40