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	$106.60	4.159%	$111.0335	$111.03	$111.05	$111.00
Purchase #2	$172.99	13.760%	$196.7934	$196.79	$196.80	$196.80
Purchase #3	$155.96	6.369%	$165.8931	$165.89	$165.90	$165.90
Purchase #4	$112.29	7.233%	$120.4119	$120.41	$120.40	$120.40
Purchase #5	$195.99	6.855%	$209.4251	$209.43	$209.45	$209.40
Purchase #6	$171.88	6.236%	$182.5984	$182.60	$182.60	$182.60
Purchase #7	$72.72	7.874%	$78.446	$78.45	$78.45	$78.40
7 purchase totals =	$988.43		$1,064.6014	$1,064.60	$1,064.65	$1,064.50