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	$93.98	6.496%	$100.0849	$100.08	$100.10	$100.10
Purchase #2	$208.95	6.242%	$221.9927	$221.99	$222.00	$222.00
Purchase #3	$83.39	6.511%	$88.8195	$88.82	$88.80	$88.80
Purchase #4	$102.71	12.436%	$115.483	$115.48	$115.50	$115.50
Purchase #5	$144.37	6.147%	$153.2444	$153.24	$153.25	$153.20
Purchase #6	$192.77	4.213%	$200.8914	$200.89	$200.90	$200.90
Purchase #7	$190.34	13.343%	$215.7371	$215.74	$215.75	$215.70
7 purchase totals =	$1,016.51		$1,096.2530	$1,096.24	$1,096.30	$1,096.20