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	$102.29	12.662%	$115.242	$115.24	$115.25	$115.20
Purchase #2	$68.64	6.538%	$73.1277	$73.13	$73.15	$73.10
Purchase #3	$130.78	11.551%	$145.8864	$145.89	$145.90	$145.90
Purchase #4	$146.27	4.339%	$152.6167	$152.62	$152.60	$152.60
Purchase #5	$61.91	3.805%	$64.2657	$64.27	$64.25	$64.30
Purchase #6	$196.55	13.112%	$222.3216	$222.32	$222.30	$222.30
Purchase #7	$169.91	10.527%	$187.7964	$187.80	$187.80	$187.80
7 purchase totals =	$876.35		$961.2565	$961.27	$961.25	$961.20