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	$230.51	6.313%	$245.0621	$245.06	$245.05	$245.10
Purchase #2	$204.76	11.848%	$229.02	$229.02	$229.00	$229.00
Purchase #3	$116.44	13.836%	$132.5506	$132.55	$132.55	$132.60
Purchase #4	$168.32	12.179%	$188.8197	$188.82	$188.80	$188.80
Purchase #5	$189.40	7.742%	$204.0633	$204.06	$204.05	$204.10
Purchase #6	$45.42	3.527%	$47.022	$47.02	$47.00	$47.00
Purchase #7	$133.82	12.296%	$150.2745	$150.27	$150.25	$150.30
7 purchase totals =	$1,088.67		$1,196.8122	$1,196.80	$1,196.70	$1,196.90