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	$168.74	5.657%	$178.2856	$178.29	$178.30	$178.30
Purchase #2	$143.54	3.440%	$148.4778	$148.48	$148.50	$148.50
Purchase #3	$28.32	11.320%	$31.5258	$31.53	$31.55	$31.50
Purchase #4	$20.32	10.217%	$22.3961	$22.40	$22.40	$22.40
Purchase #5	$174.72	5.440%	$184.2248	$184.22	$184.20	$184.20
Purchase #6	$223.86	9.171%	$244.3902	$244.39	$244.40	$244.40
Purchase #7	$214.62	4.192%	$223.6169	$223.62	$223.60	$223.60
7 purchase totals =	$974.12		$1,032.9172	$1,032.93	$1,032.95	$1,032.90