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	$148.61	5.186%	$156.3169	$156.32	$156.30	$156.30
Purchase #2	$219.69	6.349%	$233.6381	$233.64	$233.65	$233.60
Purchase #3	$11.74	9.676%	$12.876	$12.88	$12.90	$12.90
Purchase #4	$183.72	6.701%	$196.0311	$196.03	$196.05	$196.00
Purchase #5	$168.93	9.115%	$184.328	$184.33	$184.35	$184.30
Purchase #6	$49.41	7.839%	$53.2832	$53.28	$53.30	$53.30
Purchase #7	$185.54	10.507%	$205.0347	$205.03	$205.05	$205.00
7 purchase totals =	$967.64		$1,041.5080	$1,041.51	$1,041.60	$1,041.40