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	$155.77	11.756%	$174.0823	$174.08	$174.10	$174.10
Purchase #2	$186.43	4.382%	$194.5994	$194.60	$194.60	$194.60
Purchase #3	$201.91	4.153%	$210.2953	$210.30	$210.30	$210.30
Purchase #4	$122.37	7.812%	$131.9295	$131.93	$131.95	$131.90
Purchase #5	$47.90	11.288%	$53.307	$53.31	$53.30	$53.30
Purchase #6	$168.72	3.546%	$174.7028	$174.70	$174.70	$174.70
Purchase #7	$33.77	12.359%	$37.9436	$37.94	$37.95	$37.90
7 purchase totals =	$916.87		$976.8599	$976.86	$976.90	$976.80