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	$157.96	5.638%	$166.8658	$166.87	$166.85	$166.90
Purchase #2	$226.66	12.566%	$255.1421	$255.14	$255.15	$255.10
Purchase #3	$118.57	11.335%	$132.0099	$132.01	$132.00	$132.00
Purchase #4	$229.94	9.119%	$250.9082	$250.91	$250.90	$250.90
Purchase #5	$250.51	6.747%	$267.4119	$267.41	$267.40	$267.40
Purchase #6	$165.31	3.740%	$171.4926	$171.49	$171.50	$171.50
Purchase #7	$145.84	10.260%	$160.8032	$160.80	$160.80	$160.80
7 purchase totals =	$1,294.79		$1,404.6337	$1,404.63	$1,404.60	$1,404.60