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	$96.50	13.343%	$109.376	$109.38	$109.40	$109.40
Purchase #2	$44.31	3.834%	$46.0088	$46.01	$46.00	$46.00
Purchase #3	$150.57	6.201%	$159.9068	$159.91	$159.90	$159.90
Purchase #4	$36.89	10.792%	$40.8712	$40.87	$40.85	$40.90
Purchase #5	$162.31	7.747%	$174.8842	$174.88	$174.90	$174.90
Purchase #6	$204.41	13.147%	$231.2838	$231.28	$231.30	$231.30
Purchase #7	$93.68	3.108%	$96.5916	$96.59	$96.60	$96.60
7 purchase totals =	$788.67		$858.9224	$858.92	$858.95	$859.00