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	$156.79	7.827%	$169.062	$169.06	$169.05	$169.10
Purchase #2	$156.89	7.104%	$168.0355	$168.04	$168.05	$168.00
Purchase #3	$54.75	12.669%	$61.6863	$61.69	$61.70	$61.70
Purchase #4	$82.41	9.497%	$90.2365	$90.24	$90.25	$90.20
Purchase #5	$12.79	5.632%	$13.5103	$13.51	$13.50	$13.50
Purchase #6	$104.28	3.345%	$107.7682	$107.77	$107.75	$107.80
Purchase #7	$138.47	6.480%	$147.4429	$147.44	$147.45	$147.40
7 purchase totals =	$706.38		$757.7417	$757.75	$757.75	$757.70