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	$169.67	9.182%	$185.2491	$185.25	$185.25	$185.20
Purchase #2	$123.84	3.264%	$127.8821	$127.88	$127.90	$127.90
Purchase #3	$113.58	13.825%	$129.2824	$129.28	$129.30	$129.30
Purchase #4	$232.28	9.364%	$254.0307	$254.03	$254.05	$254.00
Purchase #5	$185.97	12.649%	$209.4933	$209.49	$209.50	$209.50
Purchase #6	$70.59	13.477%	$80.1034	$80.10	$80.10	$80.10
Purchase #7	$70.38	12.174%	$78.9481	$78.95	$78.95	$78.90
7 purchase totals =	$966.31		$1,064.9891	$1,064.98	$1,065.05	$1,064.90