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	$59.82	9.708%	$65.6273	$65.63	$65.65	$65.60
Purchase #2	$200.80	4.731%	$210.2998	$210.30	$210.30	$210.30
Purchase #3	$202.76	10.607%	$224.2668	$224.27	$224.25	$224.30
Purchase #4	$172.52	13.741%	$196.226	$196.23	$196.25	$196.20
Purchase #5	$132.86	6.270%	$141.1903	$141.19	$141.20	$141.20
Purchase #6	$61.48	11.134%	$68.3252	$68.33	$68.35	$68.30
Purchase #7	$94.43	5.801%	$99.9079	$99.91	$99.90	$99.90
7 purchase totals =	$924.67		$1,005.8433	$1,005.86	$1,005.90	$1,005.80