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	$164.25	13.415%	$186.2841	$186.28	$186.30	$186.30
Purchase #2	$49.36	3.872%	$51.2712	$51.27	$51.25	$51.30
Purchase #3	$113.82	8.839%	$123.8805	$123.88	$123.90	$123.90
Purchase #4	$177.33	3.865%	$184.1838	$184.18	$184.20	$184.20
Purchase #5	$32.56	9.138%	$35.5353	$35.54	$35.55	$35.50
Purchase #6	$170.86	12.460%	$192.1492	$192.15	$192.15	$192.10
Purchase #7	$135.60	12.407%	$152.4239	$152.42	$152.40	$152.40
7 purchase totals =	$843.78		$925.7280	$925.72	$925.75	$925.70