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	$71.72	10.481%	$79.237	$79.24	$79.25	$79.20
Purchase #2	$49.61	9.816%	$54.4797	$54.48	$54.50	$54.50
Purchase #3	$157.96	4.725%	$165.4236	$165.42	$165.40	$165.40
Purchase #4	$92.98	6.570%	$99.0888	$99.09	$99.10	$99.10
Purchase #5	$189.42	7.337%	$203.3177	$203.32	$203.30	$203.30
Purchase #6	$150.81	9.462%	$165.0796	$165.08	$165.10	$165.10
Purchase #7	$199.34	8.816%	$216.9138	$216.91	$216.90	$216.90
7 purchase totals =	$911.84		$983.5402	$983.54	$983.55	$983.50