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	$202.36	10.388%	$223.3812	$223.38	$223.40	$223.40
Purchase #2	$50.88	9.201%	$55.5615	$55.56	$55.55	$55.60
Purchase #3	$47.96	8.756%	$52.1594	$52.16	$52.15	$52.20
Purchase #4	$48.61	13.455%	$55.1505	$55.15	$55.15	$55.20
Purchase #5	$180.74	3.760%	$187.5358	$187.54	$187.55	$187.50
Purchase #6	$245.73	13.806%	$279.6555	$279.66	$279.65	$279.70
Purchase #7	$195.48	8.385%	$211.871	$211.87	$211.85	$211.90
7 purchase totals =	$971.76		$1,065.3149	$1,065.32	$1,065.30	$1,065.50