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	$81.74	9.214%	$89.2715	$89.27	$89.25	$89.30
Purchase #2	$174.87	4.812%	$183.2847	$183.28	$183.30	$183.30
Purchase #3	$190.71	3.766%	$197.8921	$197.89	$197.90	$197.90
Purchase #4	$94.67	4.323%	$98.7626	$98.76	$98.75	$98.80
Purchase #5	$210.98	8.365%	$228.6285	$228.63	$228.65	$228.60
Purchase #6	$51.33	6.675%	$54.7563	$54.76	$54.75	$54.80
Purchase #7	$91.59	11.248%	$101.892	$101.89	$101.90	$101.90
7 purchase totals =	$895.89		$954.4877	$954.48	$954.50	$954.60