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	$96.50	13.446%	$109.4754	$109.48	$109.50	$109.50
Purchase #2	$214.52	8.358%	$232.4496	$232.45	$232.45	$232.40
Purchase #3	$39.38	4.360%	$41.097	$41.10	$41.10	$41.10
Purchase #4	$79.54	3.276%	$82.1457	$82.15	$82.15	$82.10
Purchase #5	$222.94	6.471%	$237.3664	$237.37	$237.35	$237.40
Purchase #6	$156.95	6.116%	$166.5491	$166.55	$166.55	$166.50
Purchase #7	$196.99	11.560%	$219.762	$219.76	$219.75	$219.80
7 purchase totals =	$1,006.82		$1,088.8452	$1,088.86	$1,088.85	$1,088.80