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	$98.26	12.559%	$110.6005	$110.60	$110.60	$110.60
Purchase #2	$125.48	8.524%	$136.1759	$136.18	$136.20	$136.20
Purchase #3	$212.39	5.108%	$223.2389	$223.24	$223.25	$223.20
Purchase #4	$238.45	12.681%	$268.6878	$268.69	$268.70	$268.70
Purchase #5	$99.26	12.737%	$111.9027	$111.90	$111.90	$111.90
Purchase #6	$210.43	5.825%	$222.6875	$222.69	$222.70	$222.70
Purchase #7	$72.80	11.153%	$80.9194	$80.92	$80.90	$80.90
7 purchase totals =	$1,057.07		$1,154.2127	$1,154.22	$1,154.25	$1,154.20