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	$160.67	8.701%	$174.6499	$174.65	$174.65	$174.60
Purchase #2	$89.46	11.372%	$99.6334	$99.63	$99.65	$99.60
Purchase #3	$161.90	10.632%	$179.1132	$179.11	$179.10	$179.10
Purchase #4	$64.91	13.744%	$73.8312	$73.83	$73.85	$73.80
Purchase #5	$110.78	5.141%	$116.4752	$116.48	$116.50	$116.50
Purchase #6	$109.67	6.489%	$116.7865	$116.79	$116.80	$116.80
Purchase #7	$102.61	11.639%	$114.5528	$114.55	$114.55	$114.60
7 purchase totals =	$800.00		$875.0422	$875.04	$875.10	$875.00