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	$111.59	7.228%	$119.6557	$119.66	$119.65	$119.70
Purchase #2	$78.70	9.142%	$85.8948	$85.89	$85.90	$85.90
Purchase #3	$191.57	11.614%	$213.8189	$213.82	$213.80	$213.80
Purchase #4	$145.58	11.535%	$162.3727	$162.37	$162.35	$162.40
Purchase #5	$175.83	7.467%	$188.9592	$188.96	$188.95	$189.00
Purchase #6	$153.60	11.543%	$171.33	$171.33	$171.35	$171.30
Purchase #7	$215.28	6.401%	$229.0601	$229.06	$229.05	$229.10
7 purchase totals =	$1,072.15		$1,171.0914	$1,171.09	$1,171.05	$1,171.20