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	$130.47	12.683%	$147.0175	$147.02	$147.00	$147.00
Purchase #2	$73.69	12.173%	$82.6603	$82.66	$82.65	$82.70
Purchase #3	$77.72	8.585%	$84.3923	$84.39	$84.40	$84.40
Purchase #4	$132.36	3.109%	$136.4751	$136.48	$136.50	$136.50
Purchase #5	$141.56	9.558%	$155.0903	$155.09	$155.10	$155.10
Purchase #6	$43.89	3.459%	$45.4082	$45.41	$45.40	$45.40
Purchase #7	$12.86	11.661%	$14.3596	$14.36	$14.35	$14.40
7 purchase totals =	$612.55		$665.4033	$665.41	$665.40	$665.50