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	$179.71	12.811%	$202.7326	$202.73	$202.75	$202.70
Purchase #2	$221.40	3.683%	$229.5542	$229.55	$229.55	$229.60
Purchase #3	$13.67	4.520%	$14.2879	$14.29	$14.30	$14.30
Purchase #4	$207.25	3.528%	$214.5618	$214.56	$214.55	$214.60
Purchase #5	$80.84	11.680%	$90.2821	$90.28	$90.30	$90.30
Purchase #6	$38.98	9.187%	$42.5611	$42.56	$42.55	$42.60
Purchase #7	$90.62	10.780%	$100.3888	$100.39	$100.40	$100.40
7 purchase totals =	$832.47		$894.3685	$894.36	$894.40	$894.50