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	$61.74	11.249%	$68.6851	$68.69	$68.70	$68.70
Purchase #2	$91.86	10.330%	$101.3491	$101.35	$101.35	$101.30
Purchase #3	$190.36	5.118%	$200.1026	$200.10	$200.10	$200.10
Purchase #4	$41.46	4.512%	$43.3307	$43.33	$43.35	$43.30
Purchase #5	$212.55	10.581%	$235.0399	$235.04	$235.05	$235.00
Purchase #6	$123.33	13.500%	$139.9796	$139.98	$140.00	$140.00
Purchase #7	$52.80	12.347%	$59.3192	$59.32	$59.30	$59.30
7 purchase totals =	$774.10		$847.8062	$847.81	$847.85	$847.70