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	$212.58	6.355%	$226.0895	$226.09	$226.10	$226.10
Purchase #2	$78.91	4.435%	$82.4097	$82.41	$82.40	$82.40
Purchase #3	$45.53	5.345%	$47.9636	$47.96	$47.95	$48.00
Purchase #4	$196.94	12.846%	$222.2389	$222.24	$222.25	$222.20
Purchase #5	$146.41	9.608%	$160.4771	$160.48	$160.50	$160.50
Purchase #6	$239.32	8.148%	$258.8198	$258.82	$258.80	$258.80
Purchase #7	$235.54	6.632%	$251.161	$251.16	$251.15	$251.20
7 purchase totals =	$1,155.23		$1,249.1596	$1,249.16	$1,249.15	$1,249.20