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	$204.88	10.211%	$225.8003	$225.80	$225.80	$225.80
Purchase #2	$171.37	7.323%	$183.9194	$183.92	$183.90	$183.90
Purchase #3	$100.48	8.382%	$108.9022	$108.90	$108.90	$108.90
Purchase #4	$241.86	4.720%	$253.2758	$253.28	$253.30	$253.30
Purchase #5	$52.92	12.107%	$59.327	$59.33	$59.35	$59.30
Purchase #6	$245.85	4.178%	$256.1216	$256.12	$256.10	$256.10
Purchase #7	$31.45	6.349%	$33.4468	$33.45	$33.45	$33.40
7 purchase totals =	$1,048.81		$1,120.7931	$1,120.80	$1,120.80	$1,120.70