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	$52.49	3.450%	$54.3009	$54.30	$54.30	$54.30
Purchase #2	$54.71	13.514%	$62.1035	$62.10	$62.10	$62.10
Purchase #3	$29.41	10.379%	$32.4625	$32.46	$32.45	$32.50
Purchase #4	$96.36	13.198%	$109.0776	$109.08	$109.10	$109.10
Purchase #5	$229.45	3.709%	$237.9603	$237.96	$237.95	$238.00
Purchase #6	$205.88	10.810%	$228.1356	$228.14	$228.15	$228.10
Purchase #7	$165.68	3.273%	$171.1027	$171.10	$171.10	$171.10
7 purchase totals =	$833.98		$895.1431	$895.14	$895.15	$895.20