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	$40.69	12.839%	$45.9142	$45.91	$45.90	$45.90
Purchase #2	$113.42	12.533%	$127.6349	$127.63	$127.65	$127.60
Purchase #3	$200.64	4.872%	$210.4152	$210.42	$210.40	$210.40
Purchase #4	$92.53	6.257%	$98.3196	$98.32	$98.30	$98.30
Purchase #5	$147.35	13.671%	$167.4942	$167.49	$167.50	$167.50
Purchase #6	$145.56	11.753%	$162.6677	$162.67	$162.65	$162.70
Purchase #7	$199.94	12.519%	$224.9705	$224.97	$224.95	$225.00
7 purchase totals =	$940.13		$1,037.4163	$1,037.41	$1,037.35	$1,037.40