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	$97.49	3.310%	$100.7169	$100.72	$100.70	$100.70
Purchase #2	$142.79	9.855%	$156.862	$156.86	$156.85	$156.90
Purchase #3	$248.78	13.484%	$282.3255	$282.33	$282.35	$282.30
Purchase #4	$133.93	6.293%	$142.3582	$142.36	$142.35	$142.40
Purchase #5	$19.51	4.289%	$20.3468	$20.35	$20.35	$20.30
Purchase #6	$211.36	3.811%	$219.4149	$219.41	$219.40	$219.40
Purchase #7	$119.93	11.403%	$133.6056	$133.61	$133.60	$133.60
7 purchase totals =	$973.79		$1,055.6299	$1,055.64	$1,055.60	$1,055.60