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	$200.35	11.525%	$223.4403	$223.44	$223.45	$223.40
Purchase #2	$82.45	10.872%	$91.414	$91.41	$91.40	$91.40
Purchase #3	$38.37	7.817%	$41.3694	$41.37	$41.35	$41.40
Purchase #4	$42.37	8.796%	$46.0969	$46.10	$46.10	$46.10
Purchase #5	$86.89	6.295%	$92.3597	$92.36	$92.35	$92.40
Purchase #6	$44.90	4.385%	$46.8689	$46.87	$46.85	$46.90
Purchase #7	$134.33	12.278%	$150.823	$150.82	$150.80	$150.80
7 purchase totals =	$629.66		$692.3722	$692.37	$692.30	$692.40