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	$47.79	9.263%	$52.2168	$52.22	$52.20	$52.20
Purchase #2	$75.52	8.652%	$82.054	$82.05	$82.05	$82.10
Purchase #3	$188.57	4.329%	$196.7332	$196.73	$196.75	$196.70
Purchase #4	$147.86	11.330%	$164.6125	$164.61	$164.60	$164.60
Purchase #5	$158.92	4.423%	$165.949	$165.95	$165.95	$165.90
Purchase #6	$44.25	3.441%	$45.7726	$45.77	$45.75	$45.80
Purchase #7	$98.31	13.326%	$111.4108	$111.41	$111.40	$111.40
7 purchase totals =	$761.22		$818.7489	$818.74	$818.70	$818.70