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	$31.54	4.230%	$32.8741	$32.87	$32.85	$32.90
Purchase #2	$42.35	7.568%	$45.555	$45.56	$45.55	$45.60
Purchase #3	$223.40	12.671%	$251.707	$251.71	$251.70	$251.70
Purchase #4	$201.82	10.391%	$222.7911	$222.79	$222.80	$222.80
Purchase #5	$81.86	4.799%	$85.7885	$85.79	$85.80	$85.80
Purchase #6	$182.96	6.299%	$194.4847	$194.48	$194.50	$194.50
Purchase #7	$71.40	10.757%	$79.0805	$79.08	$79.10	$79.10
7 purchase totals =	$835.33		$912.2809	$912.28	$912.30	$912.40