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	$158.89	8.409%	$172.2511	$172.25	$172.25	$172.30
Purchase #2	$168.38	9.149%	$183.7851	$183.79	$183.80	$183.80
Purchase #3	$35.33	8.314%	$38.2673	$38.27	$38.25	$38.30
Purchase #4	$179.91	4.279%	$187.6083	$187.61	$187.60	$187.60
Purchase #5	$174.70	6.211%	$185.5506	$185.55	$185.55	$185.60
Purchase #6	$109.92	13.293%	$124.5317	$124.53	$124.55	$124.50
Purchase #7	$85.82	4.226%	$89.4468	$89.45	$89.45	$89.40
7 purchase totals =	$912.95		$981.4409	$981.45	$981.45	$981.50