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	$76.71	7.609%	$82.5469	$82.55	$82.55	$82.50
Purchase #2	$94.32	4.392%	$98.4625	$98.46	$98.45	$98.50
Purchase #3	$222.71	9.360%	$243.5557	$243.56	$243.55	$243.60
Purchase #4	$208.76	12.718%	$235.3101	$235.31	$235.30	$235.30
Purchase #5	$150.27	6.223%	$159.6213	$159.62	$159.60	$159.60
Purchase #6	$5.61	6.445%	$5.9716	$5.97	$5.95	$6.00
Purchase #7	$205.48	10.709%	$227.4849	$227.48	$227.50	$227.50
7 purchase totals =	$963.86		$1,052.9530	$1,052.95	$1,052.90	$1,053.00