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	$62.68	7.401%	$67.3189	$67.32	$67.30	$67.30
Purchase #2	$122.46	3.587%	$126.8526	$126.85	$126.85	$126.90
Purchase #3	$35.86	4.749%	$37.563	$37.56	$37.55	$37.60
Purchase #4	$27.28	5.330%	$28.734	$28.73	$28.75	$28.70
Purchase #5	$66.72	4.796%	$69.9199	$69.92	$69.90	$69.90
Purchase #6	$115.52	4.632%	$120.8709	$120.87	$120.85	$120.90
Purchase #7	$82.48	11.381%	$91.867	$91.87	$91.85	$91.90
7 purchase totals =	$513.00		$543.1263	$543.12	$543.05	$543.20