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	$55.55	7.709%	$59.8323	$59.83	$59.85	$59.80
Purchase #2	$74.30	6.132%	$78.8561	$78.86	$78.85	$78.90
Purchase #3	$165.75	10.589%	$183.3013	$183.30	$183.30	$183.30
Purchase #4	$14.90	10.185%	$16.4176	$16.42	$16.40	$16.40
Purchase #5	$39.26	9.262%	$42.8963	$42.90	$42.90	$42.90
Purchase #6	$71.26	7.616%	$76.6872	$76.69	$76.70	$76.70
Purchase #7	$104.72	13.457%	$118.8122	$118.81	$118.80	$118.80
7 purchase totals =	$525.74		$576.8030	$576.81	$576.80	$576.80