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	$138.61	8.414%	$150.2726	$150.27	$150.25	$150.30
Purchase #2	$202.41	10.150%	$222.9546	$222.95	$222.95	$223.00
Purchase #3	$135.80	10.549%	$150.1255	$150.13	$150.15	$150.10
Purchase #4	$208.93	6.433%	$222.3705	$222.37	$222.35	$222.40
Purchase #5	$49.97	6.490%	$53.2131	$53.21	$53.20	$53.20
Purchase #6	$161.66	10.469%	$178.5842	$178.58	$178.60	$178.60
Purchase #7	$108.95	4.614%	$113.977	$113.98	$114.00	$114.00
7 purchase totals =	$1,006.33		$1,091.4975	$1,091.49	$1,091.50	$1,091.60