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	$227.73	11.697%	$254.3676	$254.37	$254.35	$254.40
Purchase #2	$181.77	9.486%	$199.0127	$199.01	$199.00	$199.00
Purchase #3	$39.87	6.207%	$42.3447	$42.34	$42.35	$42.30
Purchase #4	$138.75	4.839%	$145.4641	$145.46	$145.45	$145.50
Purchase #5	$105.59	7.732%	$113.7542	$113.75	$113.75	$113.80
Purchase #6	$196.28	7.739%	$211.4701	$211.47	$211.45	$211.50
Purchase #7	$41.34	6.510%	$44.0312	$44.03	$44.05	$44.00
7 purchase totals =	$931.33		$1,010.4446	$1,010.43	$1,010.40	$1,010.50