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	$106.31	4.394%	$110.9813	$110.98	$111.00	$111.00
Purchase #2	$205.80	9.200%	$224.7336	$224.73	$224.75	$224.70
Purchase #3	$173.41	3.146%	$178.8655	$178.87	$178.85	$178.90
Purchase #4	$200.83	5.508%	$211.8917	$211.89	$211.90	$211.90
Purchase #5	$207.69	12.747%	$234.1642	$234.16	$234.15	$234.20
Purchase #6	$68.41	6.380%	$72.7746	$72.77	$72.75	$72.80
Purchase #7	$91.89	4.287%	$95.8293	$95.83	$95.85	$95.80
7 purchase totals =	$1,054.34		$1,129.2402	$1,129.23	$1,129.25	$1,129.30