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	$133.77	3.571%	$138.5469	$138.55	$138.55	$138.50
Purchase #2	$192.98	9.111%	$210.5624	$210.56	$210.55	$210.60
Purchase #3	$166.31	4.721%	$174.1615	$174.16	$174.15	$174.20
Purchase #4	$85.33	8.430%	$92.5233	$92.52	$92.50	$92.50
Purchase #5	$161.52	4.184%	$168.278	$168.28	$168.30	$168.30
Purchase #6	$246.78	9.207%	$269.501	$269.50	$269.50	$269.50
Purchase #7	$156.26	4.108%	$162.6792	$162.68	$162.70	$162.70
7 purchase totals =	$1,142.95		$1,216.2523	$1,216.25	$1,216.25	$1,216.30