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	$164.37	4.781%	$172.2285	$172.23	$172.25	$172.20
Purchase #2	$156.77	9.212%	$171.2117	$171.21	$171.20	$171.20
Purchase #3	$53.43	3.237%	$55.1595	$55.16	$55.15	$55.20
Purchase #4	$189.97	12.184%	$213.1159	$213.12	$213.10	$213.10
Purchase #5	$67.40	7.445%	$72.4179	$72.42	$72.40	$72.40
Purchase #6	$72.99	6.453%	$77.7	$77.70	$77.70	$77.70
Purchase #7	$63.98	5.498%	$67.4976	$67.50	$67.50	$67.50
7 purchase totals =	$768.91		$829.3311	$829.34	$829.30	$829.30