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	$130.78	9.791%	$143.5847	$143.58	$143.60	$143.60
Purchase #2	$98.28	13.742%	$111.7856	$111.79	$111.80	$111.80
Purchase #3	$62.90	3.190%	$64.9065	$64.91	$64.90	$64.90
Purchase #4	$102.82	12.554%	$115.728	$115.73	$115.75	$115.70
Purchase #5	$81.50	9.354%	$89.1235	$89.12	$89.10	$89.10
Purchase #6	$144.51	12.457%	$162.5116	$162.51	$162.50	$162.50
Purchase #7	$193.57	9.459%	$211.8798	$211.88	$211.90	$211.90
7 purchase totals =	$814.36		$899.5197	$899.52	$899.55	$899.50