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	$43.95	3.300%	$45.4004	$45.40	$45.40	$45.40
Purchase #2	$109.27	3.231%	$112.8005	$112.80	$112.80	$112.80
Purchase #3	$125.81	6.427%	$133.8958	$133.90	$133.90	$133.90
Purchase #4	$89.77	10.207%	$98.9328	$98.93	$98.95	$98.90
Purchase #5	$148.61	11.679%	$165.9662	$165.97	$165.95	$166.00
Purchase #6	$150.72	9.535%	$165.0912	$165.09	$165.10	$165.10
Purchase #7	$79.35	11.765%	$88.6855	$88.69	$88.70	$88.70
7 purchase totals =	$747.48		$810.7724	$810.78	$810.80	$810.80