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	$245.79	13.462%	$278.8782	$278.88	$278.90	$278.90
Purchase #2	$187.54	4.563%	$196.0975	$196.10	$196.10	$196.10
Purchase #3	$59.62	11.122%	$66.2509	$66.25	$66.25	$66.30
Purchase #4	$79.77	7.380%	$85.657	$85.66	$85.65	$85.70
Purchase #5	$58.29	7.557%	$62.695	$62.70	$62.70	$62.70
Purchase #6	$87.77	4.662%	$91.8618	$91.86	$91.85	$91.90
Purchase #7	$215.96	13.833%	$245.8337	$245.83	$245.85	$245.80
7 purchase totals =	$934.74		$1,027.2741	$1,027.28	$1,027.30	$1,027.40