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	$184.82	13.235%	$209.2809	$209.28	$209.30	$209.30
Purchase #2	$56.69	4.174%	$59.0562	$59.06	$59.05	$59.10
Purchase #3	$34.63	10.801%	$38.3704	$38.37	$38.35	$38.40
Purchase #4	$54.75	7.581%	$58.9006	$58.90	$58.90	$58.90
Purchase #5	$187.56	6.168%	$199.1287	$199.13	$199.15	$199.10
Purchase #6	$186.66	5.474%	$196.8778	$196.88	$196.90	$196.90
Purchase #7	$202.86	5.247%	$213.5041	$213.50	$213.50	$213.50
7 purchase totals =	$907.97		$975.1187	$975.12	$975.15	$975.20