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	$158.33	7.341%	$169.953	$169.95	$169.95	$170.00
Purchase #2	$64.57	10.197%	$71.1542	$71.15	$71.15	$71.20
Purchase #3	$117.97	11.675%	$131.743	$131.74	$131.75	$131.70
Purchase #4	$163.83	13.607%	$186.1223	$186.12	$186.10	$186.10
Purchase #5	$99.61	12.400%	$111.9616	$111.96	$111.95	$112.00
Purchase #6	$222.42	3.325%	$229.8155	$229.82	$229.80	$229.80
Purchase #7	$232.36	7.330%	$249.392	$249.39	$249.40	$249.40
7 purchase totals =	$1,059.09		$1,150.1416	$1,150.13	$1,150.10	$1,150.20