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	$127.49	5.841%	$134.9367	$134.94	$134.95	$134.90
Purchase #2	$173.96	4.220%	$181.3011	$181.30	$181.30	$181.30
Purchase #3	$106.65	4.565%	$111.5186	$111.52	$111.50	$111.50
Purchase #4	$233.26	4.646%	$244.0973	$244.10	$244.10	$244.10
Purchase #5	$242.50	5.380%	$255.5465	$255.55	$255.55	$255.50
Purchase #6	$142.86	13.752%	$162.5061	$162.51	$162.50	$162.50
Purchase #7	$132.53	11.454%	$147.71	$147.71	$147.70	$147.70
7 purchase totals =	$1,159.25		$1,237.6163	$1,237.63	$1,237.60	$1,237.50