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	$199.47	5.278%	$209.998	$210.00	$210.00	$210.00
Purchase #2	$159.92	12.808%	$180.4026	$180.40	$180.40	$180.40
Purchase #3	$86.41	4.589%	$90.3754	$90.38	$90.40	$90.40
Purchase #4	$142.48	3.681%	$147.7247	$147.72	$147.70	$147.70
Purchase #5	$32.50	8.266%	$35.1865	$35.19	$35.20	$35.20
Purchase #6	$27.90	11.273%	$31.0452	$31.05	$31.05	$31.00
Purchase #7	$35.79	7.801%	$38.582	$38.58	$38.60	$38.60
7 purchase totals =	$684.47		$733.3144	$733.32	$733.35	$733.30