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	$184.51	6.247%	$196.0363	$196.04	$196.05	$196.00
Purchase #2	$82.37	11.572%	$91.9019	$91.90	$91.90	$91.90
Purchase #3	$199.38	6.474%	$212.2879	$212.29	$212.30	$212.30
Purchase #4	$226.88	12.249%	$254.6705	$254.67	$254.65	$254.70
Purchase #5	$43.52	5.490%	$45.9092	$45.91	$45.90	$45.90
Purchase #6	$163.93	3.387%	$169.4823	$169.48	$169.50	$169.50
Purchase #7	$241.27	3.270%	$249.1595	$249.16	$249.15	$249.20
7 purchase totals =	$1,141.86		$1,219.4476	$1,219.45	$1,219.45	$1,219.50