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	$114.92	12.187%	$128.9253	$128.93	$128.95	$128.90
Purchase #2	$79.76	6.812%	$85.1933	$85.19	$85.20	$85.20
Purchase #3	$47.44	11.815%	$53.045	$53.05	$53.05	$53.00
Purchase #4	$112.56	3.627%	$116.6426	$116.64	$116.65	$116.60
Purchase #5	$120.41	11.622%	$134.4041	$134.40	$134.40	$134.40
Purchase #6	$67.67	7.778%	$72.9334	$72.93	$72.95	$72.90
Purchase #7	$101.64	12.442%	$114.286	$114.29	$114.30	$114.30
7 purchase totals =	$644.40		$705.4297	$705.43	$705.50	$705.30