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	$106.51	4.311%	$111.1016	$111.10	$111.10	$111.10
Purchase #2	$36.83	4.850%	$38.6163	$38.62	$38.60	$38.60
Purchase #3	$213.92	13.268%	$242.3029	$242.30	$242.30	$242.30
Purchase #4	$135.46	9.499%	$148.3273	$148.33	$148.35	$148.30
Purchase #5	$214.38	6.774%	$228.9021	$228.90	$228.90	$228.90
Purchase #6	$228.36	9.354%	$249.7208	$249.72	$249.70	$249.70
Purchase #7	$179.67	3.137%	$185.3062	$185.31	$185.30	$185.30
7 purchase totals =	$1,115.13		$1,204.2772	$1,204.28	$1,204.25	$1,204.20