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	$89.99	4.740%	$94.2555	$94.26	$94.25	$94.30
Purchase #2	$49.77	10.665%	$55.078	$55.08	$55.10	$55.10
Purchase #3	$245.34	5.866%	$259.7316	$259.73	$259.75	$259.70
Purchase #4	$155.96	11.783%	$174.3368	$174.34	$174.35	$174.30
Purchase #5	$171.49	6.139%	$182.0178	$182.02	$182.00	$182.00
Purchase #6	$86.30	4.148%	$89.8797	$89.88	$89.90	$89.90
Purchase #7	$173.90	4.500%	$181.7255	$181.73	$181.75	$181.70
7 purchase totals =	$972.75		$1,037.0249	$1,037.04	$1,037.10	$1,037.00