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	$195.30	9.204%	$213.2754	$213.28	$213.30	$213.30
Purchase #2	$103.61	8.233%	$112.1402	$112.14	$112.15	$112.10
Purchase #3	$186.48	13.625%	$211.8879	$211.89	$211.90	$211.90
Purchase #4	$87.46	3.270%	$90.3199	$90.32	$90.30	$90.30
Purchase #5	$100.55	8.849%	$109.4477	$109.45	$109.45	$109.40
Purchase #6	$247.91	13.502%	$281.3828	$281.38	$281.40	$281.40
Purchase #7	$34.87	3.283%	$36.0148	$36.01	$36.00	$36.00
7 purchase totals =	$956.18		$1,054.4687	$1,054.47	$1,054.50	$1,054.40