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	$105.70	5.341%	$111.3454	$111.35	$111.35	$111.30
Purchase #2	$125.95	12.790%	$142.059	$142.06	$142.05	$142.10
Purchase #3	$225.42	3.619%	$233.5779	$233.58	$233.60	$233.60
Purchase #4	$42.30	6.571%	$45.0795	$45.08	$45.10	$45.10
Purchase #5	$76.77	3.581%	$79.5191	$79.52	$79.50	$79.50
Purchase #6	$163.38	4.726%	$171.1013	$171.10	$171.10	$171.10
Purchase #7	$136.69	3.432%	$141.3812	$141.38	$141.40	$141.40
7 purchase totals =	$876.21		$924.0634	$924.07	$924.10	$924.10