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	$102.82	9.237%	$112.3175	$112.32	$112.30	$112.30
Purchase #2	$148.42	13.787%	$168.8827	$168.88	$168.90	$168.90
Purchase #3	$129.89	10.276%	$143.2375	$143.24	$143.25	$143.20
Purchase #4	$211.85	13.373%	$240.1807	$240.18	$240.20	$240.20
Purchase #5	$54.26	3.571%	$56.1976	$56.20	$56.20	$56.20
Purchase #6	$233.88	3.319%	$241.6425	$241.64	$241.65	$241.60
Purchase #7	$139.35	6.757%	$148.7659	$148.77	$148.75	$148.80
7 purchase totals =	$1,020.47		$1,111.2244	$1,111.23	$1,111.25	$1,111.20