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	$124.78	7.172%	$133.7292	$133.73	$133.75	$133.70
Purchase #2	$180.97	7.337%	$194.2478	$194.25	$194.25	$194.20
Purchase #3	$164.43	8.502%	$178.4098	$178.41	$178.40	$178.40
Purchase #4	$70.27	10.386%	$77.5682	$77.57	$77.55	$77.60
Purchase #5	$229.92	10.435%	$253.9122	$253.91	$253.90	$253.90
Purchase #6	$78.27	4.132%	$81.5041	$81.50	$81.50	$81.50
Purchase #7	$170.50	11.611%	$190.2968	$190.30	$190.30	$190.30
7 purchase totals =	$1,019.14		$1,109.6681	$1,109.67	$1,109.65	$1,109.60