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	$106.32	7.860%	$114.6768	$114.68	$114.70	$114.70
Purchase #2	$63.68	11.868%	$71.2375	$71.24	$71.25	$71.20
Purchase #3	$101.55	4.840%	$106.465	$106.47	$106.45	$106.50
Purchase #4	$147.59	13.685%	$167.7877	$167.79	$167.80	$167.80
Purchase #5	$250.27	8.658%	$271.9384	$271.94	$271.95	$271.90
Purchase #6	$29.44	13.861%	$33.5207	$33.52	$33.50	$33.50
Purchase #7	$29.52	13.288%	$33.4426	$33.44	$33.45	$33.40
7 purchase totals =	$728.37		$799.0687	$799.08	$799.10	$799.00