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	$84.86	5.115%	$89.2006	$89.20	$89.20	$89.20
Purchase #2	$203.89	3.269%	$210.5552	$210.56	$210.55	$210.60
Purchase #3	$84.87	6.829%	$90.6658	$90.67	$90.65	$90.70
Purchase #4	$106.37	5.564%	$112.2884	$112.29	$112.30	$112.30
Purchase #5	$192.49	9.263%	$210.3203	$210.32	$210.30	$210.30
Purchase #6	$133.55	13.802%	$151.9826	$151.98	$152.00	$152.00
Purchase #7	$124.31	9.821%	$136.5185	$136.52	$136.50	$136.50
7 purchase totals =	$930.34		$1,001.5314	$1,001.54	$1,001.50	$1,001.60