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	$43.56	4.131%	$45.3595	$45.36	$45.35	$45.40
Purchase #2	$81.54	9.612%	$89.3776	$89.38	$89.40	$89.40
Purchase #3	$198.92	12.524%	$223.8327	$223.83	$223.85	$223.80
Purchase #4	$69.91	12.531%	$78.6704	$78.67	$78.65	$78.70
Purchase #5	$113.64	11.432%	$126.6313	$126.63	$126.65	$126.60
Purchase #6	$238.61	6.604%	$254.3678	$254.37	$254.35	$254.40
Purchase #7	$117.45	7.518%	$126.2799	$126.28	$126.30	$126.30
7 purchase totals =	$863.63		$944.5192	$944.52	$944.55	$944.60