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	$236.33	10.658%	$261.5181	$261.52	$261.50	$261.50
Purchase #2	$78.40	6.571%	$83.5517	$83.55	$83.55	$83.60
Purchase #3	$129.27	7.673%	$139.1889	$139.19	$139.20	$139.20
Purchase #4	$160.64	5.306%	$169.1636	$169.16	$169.15	$169.20
Purchase #5	$168.49	6.432%	$179.3273	$179.33	$179.35	$179.30
Purchase #6	$95.45	4.107%	$99.3701	$99.37	$99.35	$99.40
Purchase #7	$196.56	7.580%	$211.4592	$211.46	$211.45	$211.50
7 purchase totals =	$1,065.14		$1,143.5789	$1,143.58	$1,143.55	$1,143.70