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	$149.87	4.673%	$156.8734	$156.87	$156.85	$156.90
Purchase #2	$85.64	7.810%	$92.3285	$92.33	$92.35	$92.30
Purchase #3	$64.37	12.797%	$72.6074	$72.61	$72.60	$72.60
Purchase #4	$247.54	4.256%	$258.0753	$258.08	$258.10	$258.10
Purchase #5	$178.97	3.346%	$184.9583	$184.96	$184.95	$185.00
Purchase #6	$105.44	3.871%	$109.5216	$109.52	$109.50	$109.50
Purchase #7	$186.93	5.365%	$196.9588	$196.96	$196.95	$197.00
7 purchase totals =	$1,018.76		$1,071.3233	$1,071.33	$1,071.30	$1,071.40