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	$147.33	3.357%	$152.2759	$152.28	$152.30	$152.30
Purchase #2	$96.44	3.689%	$99.9977	$100.00	$100.00	$100.00
Purchase #3	$12.60	3.720%	$13.0687	$13.07	$13.05	$13.10
Purchase #4	$29.80	10.461%	$32.9174	$32.92	$32.90	$32.90
Purchase #5	$178.95	13.453%	$203.0241	$203.02	$203.00	$203.00
Purchase #6	$89.60	9.139%	$97.7885	$97.79	$97.80	$97.80
Purchase #7	$79.83	13.748%	$90.805	$90.81	$90.80	$90.80
7 purchase totals =	$634.55		$689.8773	$689.89	$689.85	$689.90