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	$72.25	8.131%	$78.1246	$78.12	$78.10	$78.10
Purchase #2	$83.66	8.743%	$90.9744	$90.97	$90.95	$91.00
Purchase #3	$241.99	7.326%	$259.7182	$259.72	$259.70	$259.70
Purchase #4	$238.90	11.370%	$266.0629	$266.06	$266.05	$266.10
Purchase #5	$174.59	9.409%	$191.0172	$191.02	$191.00	$191.00
Purchase #6	$9.28	10.696%	$10.2726	$10.27	$10.25	$10.30
Purchase #7	$151.44	7.249%	$162.4179	$162.42	$162.40	$162.40
7 purchase totals =	$972.11		$1,058.5878	$1,058.58	$1,058.45	$1,058.60