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	$210.86	10.545%	$233.0952	$233.10	$233.10	$233.10
Purchase #2	$131.49	12.414%	$147.8132	$147.81	$147.80	$147.80
Purchase #3	$123.61	3.153%	$127.5074	$127.51	$127.50	$127.50
Purchase #4	$28.95	8.740%	$31.4802	$31.48	$31.50	$31.50
Purchase #5	$109.55	5.650%	$115.7396	$115.74	$115.75	$115.70
Purchase #6	$97.59	7.179%	$104.596	$104.60	$104.60	$104.60
Purchase #7	$182.42	13.328%	$206.7329	$206.73	$206.75	$206.70
7 purchase totals =	$884.47		$966.9645	$966.97	$967.00	$966.90