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	$176.47	5.196%	$185.6394	$185.64	$185.65	$185.60
Purchase #2	$158.46	11.308%	$176.3787	$176.38	$176.40	$176.40
Purchase #3	$68.97	5.331%	$72.6468	$72.65	$72.65	$72.60
Purchase #4	$147.95	7.738%	$159.3984	$159.40	$159.40	$159.40
Purchase #5	$74.40	6.581%	$79.2963	$79.30	$79.30	$79.30
Purchase #6	$78.46	4.541%	$82.0229	$82.02	$82.00	$82.00
Purchase #7	$171.73	8.580%	$186.4644	$186.46	$186.45	$186.50
7 purchase totals =	$876.44		$941.8469	$941.85	$941.85	$941.80