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	$91.80	3.242%	$94.7762	$94.78	$94.80	$94.80
Purchase #2	$151.58	3.340%	$156.6428	$156.64	$156.65	$156.60
Purchase #3	$80.32	7.730%	$86.5287	$86.53	$86.55	$86.50
Purchase #4	$152.72	6.117%	$162.0619	$162.06	$162.05	$162.10
Purchase #5	$175.52	11.704%	$196.0629	$196.06	$196.05	$196.10
Purchase #6	$107.53	12.420%	$120.8852	$120.89	$120.90	$120.90
Purchase #7	$25.67	6.711%	$27.3927	$27.39	$27.40	$27.40
7 purchase totals =	$785.14		$844.3504	$844.35	$844.40	$844.40