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	$240.71	6.165%	$255.5498	$255.55	$255.55	$255.50
Purchase #2	$52.91	11.632%	$59.0645	$59.06	$59.05	$59.10
Purchase #3	$174.43	11.142%	$193.865	$193.87	$193.85	$193.90
Purchase #4	$166.52	10.394%	$183.8281	$183.83	$183.85	$183.80
Purchase #5	$22.95	13.183%	$25.9755	$25.98	$26.00	$26.00
Purchase #6	$186.33	9.439%	$203.9177	$203.92	$203.90	$203.90
Purchase #7	$75.80	13.267%	$85.8564	$85.86	$85.85	$85.90
7 purchase totals =	$919.65		$1,008.0570	$1,008.07	$1,008.05	$1,008.10