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	$244.37	10.199%	$269.2933	$269.29	$269.30	$269.30
Purchase #2	$200.88	10.554%	$222.0809	$222.08	$222.10	$222.10
Purchase #3	$81.59	9.146%	$89.0522	$89.05	$89.05	$89.10
Purchase #4	$190.36	12.635%	$214.412	$214.41	$214.40	$214.40
Purchase #5	$162.58	6.577%	$173.2729	$173.27	$173.25	$173.30
Purchase #6	$9.94	3.223%	$10.2604	$10.26	$10.25	$10.30
Purchase #7	$90.33	4.193%	$94.1175	$94.12	$94.10	$94.10
7 purchase totals =	$980.05		$1,072.4892	$1,072.48	$1,072.45	$1,072.60