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	$117.30	6.685%	$125.1415	$125.14	$125.15	$125.10
Purchase #2	$104.36	13.640%	$118.5947	$118.59	$118.60	$118.60
Purchase #3	$98.55	13.621%	$111.9735	$111.97	$111.95	$112.00
Purchase #4	$186.70	5.501%	$196.9704	$196.97	$196.95	$197.00
Purchase #5	$11.88	11.444%	$13.2395	$13.24	$13.25	$13.20
Purchase #6	$144.90	4.500%	$151.4205	$151.42	$151.40	$151.40
Purchase #7	$34.65	5.593%	$36.588	$36.59	$36.60	$36.60
7 purchase totals =	$698.34		$753.9281	$753.92	$753.90	$753.90