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	$225.91	10.830%	$250.3761	$250.38	$250.40	$250.40
Purchase #2	$205.81	9.766%	$225.9094	$225.91	$225.90	$225.90
Purchase #3	$58.44	12.700%	$65.8619	$65.86	$65.85	$65.90
Purchase #4	$128.73	3.627%	$133.399	$133.40	$133.40	$133.40
Purchase #5	$54.35	7.309%	$58.3224	$58.32	$58.30	$58.30
Purchase #6	$114.61	3.382%	$118.4861	$118.49	$118.50	$118.50
Purchase #7	$174.58	6.409%	$185.7688	$185.77	$185.75	$185.80
7 purchase totals =	$962.43		$1,038.1237	$1,038.13	$1,038.10	$1,038.20