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	$246.61	3.474%	$255.1772	$255.18	$255.20	$255.20
Purchase #2	$5.87	7.435%	$6.3064	$6.31	$6.30	$6.30
Purchase #3	$85.65	12.204%	$96.1027	$96.10	$96.10	$96.10
Purchase #4	$31.35	3.316%	$32.3896	$32.39	$32.40	$32.40
Purchase #5	$79.87	4.593%	$83.5384	$83.54	$83.55	$83.50
Purchase #6	$53.29	13.789%	$60.6382	$60.64	$60.65	$60.60
Purchase #7	$161.97	5.800%	$171.3643	$171.36	$171.35	$171.40
7 purchase totals =	$664.61		$705.5168	$705.52	$705.55	$705.50